Merge branch 'kstat'

This branch updates several of the zfs kstats to take advantage
of the improved raw kstat functionality.  In addition, two new
kstats and a script called dbufstat.py are introduced.

Updated+New Kstats
* dbufs        - Stats for all dbufs in the dbuf_hash
* <pool>/txgs  - Stats for the last N txgs synced to disk
* <pool>/reads - Stats for rhe last N reads issues by the ARC
* <pool>/dmu_tx_assign - Histogram of tx assign times

Signed-off-by: Brian Behlendorf <[email protected]>

27 files changed, 1653 insertions, 326 deletions

diff --git a/cmd/Makefile.am b/cmd/Makefile.am
index bad1af63e..4c3e4bbb2 100644
--- a/cmd/Makefile.am
+++ b/cmd/Makefile.am
@@ -1,2 +1,2 @@
 SUBDIRS  = zfs zpool zdb zhack zinject zstreamdump ztest zpios
-SUBDIRS += mount_zfs fsck_zfs zvol_id vdev_id arcstat
+SUBDIRS += mount_zfs fsck_zfs zvol_id vdev_id arcstat dbufstat
diff --git a/cmd/arcstat/arcstat.py b/cmd/arcstat/arcstat.py
index e01dd8b4c..f703e33cd 100755
--- a/cmd/arcstat/arcstat.py
+++ b/cmd/arcstat/arcstat.py
@@ -106,7 +106,7 @@ opfile = None
 sep = "  "              # Default separator is 2 spaces
 version = "0.4"
 l2exist = False
-cmd = ("Usage: arcstat [-hvx] [-f fields] [-o file] [-s string] [interval "
+cmd = ("Usage: arcstat.py [-hvx] [-f fields] [-o file] [-s string] [interval "
     "[count]]\n")
 cur = {}
 d = {}
@@ -136,10 +136,10 @@ def usage():
     sys.stderr.write("\t -s : Override default field separator with custom "
         "character or string\n")
     sys.stderr.write("\nExamples:\n")
-    sys.stderr.write("\tarcstat -o /tmp/a.log 2 10\n")
-    sys.stderr.write("\tarcstat -s \",\" -o /tmp/a.log 2 10\n")
-    sys.stderr.write("\tarcstat -v\n")
-    sys.stderr.write("\tarcstat -f time,hit%,dh%,ph%,mh% 1\n")
+    sys.stderr.write("\tarcstat.py -o /tmp/a.log 2 10\n")
+    sys.stderr.write("\tarcstat.py -s \",\" -o /tmp/a.log 2 10\n")
+    sys.stderr.write("\tarcstat.py -v\n")
+    sys.stderr.write("\tarcstat.py -f time,hit%,dh%,ph%,mh% 1\n")
     sys.stderr.write("\n")
 
     sys.exit(1)
diff --git a/cmd/dbufstat/Makefile.am b/cmd/dbufstat/Makefile.am
new file mode 100644
index 000000000..0548b240c
--- /dev/null
+++ b/cmd/dbufstat/Makefile.am
@@ -0,0 +1,2 @@
+bin_SCRIPTS = dbufstat.py
+EXTRA_DIST = $(bin_SCRIPTS)
diff --git a/cmd/dbufstat/dbufstat.py b/cmd/dbufstat/dbufstat.py
new file mode 100755
index 000000000..80569b1d4
--- /dev/null
+++ b/cmd/dbufstat/dbufstat.py
@@ -0,0 +1,535 @@
+#!/usr/bin/python
+#
+# Print out statistics for all cached dmu buffers.  This information
+# is available through the dbufs kstat and may be post-processed as
+# needed by the script.
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License, Version 1.0 only
+# (the "License").  You may not use this file except in compliance
+# with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+# Copyright (C) 2013 Lawrence Livermore National Security, LLC.
+# Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
+#
+
+import sys
+import getopt
+import errno
+
+bhdr  = ["pool", "objset", "object", "level", "blkid", "offset", "dbsize"]
+bxhdr = ["pool", "objset", "object", "level", "blkid", "offset", "dbsize",
+    "meta", "state", "dbholds", "list", "atype", "index", "flags", "count",
+    "asize", "access", "mru", "gmru", "mfu", "gmfu", "l2", "l2_dattr",
+    "l2_asize", "l2_comp", "aholds", "dtype", "btype", "data_bs", "meta_bs",
+    "bsize", "lvls", "dholds", "blocks", "dsize"]
+bincompat = ["cached", "direct", "indirect", "bonus", "spill"]
+
+dhdr  = ["pool", "objset", "object", "dtype", "cached"]
+dxhdr = ["pool", "objset", "object", "dtype", "btype", "data_bs", "meta_bs",
+    "bsize", "lvls", "dholds", "blocks", "dsize", "cached", "direct",
+    "indirect", "bonus", "spill"]
+dincompat = ["level", "blkid", "offset", "dbsize", "meta", "state", "dbholds",
+    "list", "atype", "index", "flags", "count", "asize", "access", "mru",
+    "gmru", "mfu", "gmfu", "l2", "l2_dattr", "l2_asize", "l2_comp", "aholds"]
+
+thdr  = ["pool", "objset", "dtype", "cached"]
+txhdr = ["pool", "objset", "dtype", "cached", "direct", "indirect",
+    "bonus", "spill"]
+tincompat = ["object", "level", "blkid", "offset", "dbsize", "meta", "state",
+    "dbholds", "list", "atype", "index", "flags", "count", "asize", "access",
+    "mru", "gmru", "mfu", "gmfu", "l2", "l2_dattr", "l2_asize", "l2_comp",
+    "aholds", "btype", "data_bs", "meta_bs", "bsize", "lvls", "dholds",
+    "blocks", "dsize"]
+
+cols = {
+    # hdr:        [size, scale, description]
+    "pool":       [15,   -1, "pool name"],
+    "objset":     [6,    -1, "dataset identification number"],
+    "object":     [10,   -1, "object number"],
+    "level":      [5,    -1, "indirection level of buffer"],
+    "blkid":      [8,    -1, "block number of buffer"],
+    "offset":     [12, 1024, "offset in object of buffer"],
+    "dbsize":     [7,  1024, "size of buffer"],
+    "meta":       [4,    -1, "is this buffer metadata?"],
+    "state":      [5,    -1, "state of buffer (read, cached, etc)"],
+    "dbholds":    [7,  1000, "number of holds on buffer"],
+    "list":       [4,    -1, "which ARC list contains this buffer"],
+    "atype":      [7,    -1, "ARC header type (data or metadata)"],
+    "index":      [5,    -1, "buffer's index into its ARC list"],
+    "flags":      [8,    -1, "ARC read flags"],
+    "count":      [5,    -1, "ARC data count"],
+    "asize":      [7,  1024, "size of this ARC buffer"],
+    "access":     [10,   -1, "time this ARC buffer was last accessed"],
+    "mru":        [5,  1000, "hits while on the ARC's MRU list"],
+    "gmru":       [5,  1000, "hits while on the ARC's MRU ghost list"],
+    "mfu":        [5,  1000, "hits while on the ARC's MFU list"],
+    "gmfu":       [5,  1000, "hits while on the ARC's MFU ghost list"],
+    "l2":         [5,  1000, "hits while on the L2ARC"],
+    "l2_dattr":   [8,    -1, "L2ARC disk address/offset"],
+    "l2_asize":   [8,  1024, "L2ARC alloc'd size (depending on compression)"],
+    "l2_comp":    [21,   -1, "L2ARC compression algorithm for buffer"],
+    "aholds":     [6,  1000, "number of holds on this ARC buffer"],
+    "dtype":      [27,   -1, "dnode type"],
+    "btype":      [27,   -1, "bonus buffer type"],
+    "data_bs":    [7,  1024, "data block size"],
+    "meta_bs":    [7,  1024, "metadata block size"],
+    "bsize":      [6,  1024, "bonus buffer size"],
+    "lvls":       [6,    -1, "number of indirection levels"],
+    "dholds":     [6,  1000, "number of holds on dnode"],
+    "blocks":     [8,  1000, "number of allocated blocks"],
+    "dsize":      [12, 1024, "size of dnode"],
+    "cached":     [6,  1024, "bytes cached for all blocks"],
+    "direct":     [6,  1024, "bytes cached for direct blocks"],
+    "indirect":   [8,  1024, "bytes cached for indirect blocks"],
+    "bonus":      [5,  1024, "bytes cached for bonus buffer"],
+    "spill":      [5,  1024, "bytes cached for spill block"],
+}
+
+hdr  = None
+xhdr = None
+sep = "  " # Default separator is 2 spaces
+cmd = ("Usage: dbufstat.py [-bdhrtvx] [-i file] [-f fields] [-o file] "
+    "[-s string]\n")
+raw = 0
+
+def print_incompat_helper(incompat):
+    cnt = 0
+    for key in sorted(incompat):
+        if cnt is 0:
+            sys.stderr.write("\t")
+        elif cnt > 8:
+            sys.stderr.write(",\n\t")
+            cnt = 0
+        else:
+            sys.stderr.write(", ")
+
+        sys.stderr.write("%s" % key)
+        cnt += 1
+
+    sys.stderr.write("\n\n")
+
+def detailed_usage():
+    sys.stderr.write("%s\n" % cmd)
+
+    sys.stderr.write("Field definitions incompatible with '-b' option:\n")
+    print_incompat_helper(bincompat)
+
+    sys.stderr.write("Field definitions incompatible with '-d' option:\n")
+    print_incompat_helper(dincompat)
+
+    sys.stderr.write("Field definitions incompatible with '-t' option:\n")
+    print_incompat_helper(tincompat)
+
+    sys.stderr.write("Field definitions are as follows:\n")
+    for key in sorted(cols.keys()):
+        sys.stderr.write("%11s : %s\n" % (key, cols[key][2]))
+    sys.stderr.write("\n")
+
+    sys.exit(1)
+
+def usage():
+    sys.stderr.write("%s\n" % cmd)
+    sys.stderr.write("\t -b : Print table of information for each dbuf\n")
+    sys.stderr.write("\t -d : Print table of information for each dnode\n")
+    sys.stderr.write("\t -h : Print this help message\n")
+    sys.stderr.write("\t -r : Print raw values\n")
+    sys.stderr.write("\t -t : Print table of information for each dnode type\n")
+    sys.stderr.write("\t -v : List all possible field headers and definitions"
+        "\n")
+    sys.stderr.write("\t -x : Print extended stats\n")
+    sys.stderr.write("\t -i : Redirect input from the specified file\n")
+    sys.stderr.write("\t -f : Specify specific fields to print (see -v)\n")
+    sys.stderr.write("\t -o : Redirect output to the specified file\n")
+    sys.stderr.write("\t -s : Override default field separator with custom "
+        "character or string\n")
+    sys.stderr.write("\nExamples:\n")
+    sys.stderr.write("\tdbufstat.py -d -o /tmp/d.log\n")
+    sys.stderr.write("\tdbufstat.py -t -s \",\" -o /tmp/t.log\n")
+    sys.stderr.write("\tdbufstat.py -v\n")
+    sys.stderr.write("\tdbufstat.py -d -f pool,object,objset,dsize,cached\n")
+    sys.stderr.write("\n")
+
+    sys.exit(1)
+
+def prettynum(sz, scale, num=0):
+    global raw
+
+    suffix = [' ', 'K', 'M', 'G', 'T', 'P', 'E', 'Z']
+    index = 0
+    save = 0
+
+    if raw or scale == -1:
+        return "%*s" % (sz, num)
+
+    # Rounding error, return 0
+    elif num > 0 and num < 1:
+        num = 0
+
+    while num > scale and index < 5:
+        save = num
+        num = num / scale
+        index += 1
+
+    if index == 0:
+        return "%*d" % (sz, num)
+
+    if (save / scale) < 10:
+        return "%*.1f%s" % (sz - 1, num, suffix[index])
+    else:
+        return "%*d%s" % (sz - 1, num, suffix[index])
+
+def print_values(v):
+    global hdr
+    global sep
+
+    try:
+        for col in hdr:
+            sys.stdout.write("%s%s" % (
+                prettynum(cols[col][0], cols[col][1], v[col]), sep))
+        sys.stdout.write("\n")
+    except IOError as e:
+        if e.errno == errno.EPIPE:
+            sys.exit(1)
+
+def print_header():
+    global hdr
+    global sep
+
+    try:
+        for col in hdr:
+            sys.stdout.write("%*s%s" % (cols[col][0], col, sep))
+        sys.stdout.write("\n")
+    except IOError as e:
+        if e.errno == errno.EPIPE:
+            sys.exit(1)
+
+def get_typestring(t):
+    type_strings = ["DMU_OT_NONE",
+        # general:
+        "DMU_OT_OBJECT_DIRECTORY", "DMU_OT_OBJECT_ARRAY",
+        "DMU_OT_PACKED_NVLIST", "DMU_OT_PACKED_NVLIST_SIZE",
+        "DMU_OT_BPOBJ", "DMU_OT_BPOBJ_HDR",
+        # spa:
+        "DMU_OT_SPACE_MAP_HEADER", "DMU_OT_SPACE_MAP",
+        # zil:
+        "DMU_OT_INTENT_LOG",
+        # dmu:
+        "DMU_OT_DNODE", "DMU_OT_OBJSET",
+        # dsl:
+        "DMU_OT_DSL_DIR", "DMU_OT_DSL_DIR_CHILD_MAP",
+        "DMU_OT_DSL_DS_SNAP_MAP", "DMU_OT_DSL_PROPS",
+        "DMU_OT_DSL_DATASET",
+        # zpl:
+        "DMU_OT_ZNODE", "DMU_OT_OLDACL", "DMU_OT_PLAIN_FILE_CONTENTS",
+        "DMU_OT_DIRECTORY_CONTENTS", "DMU_OT_MASTER_NODE",
+        "DMU_OT_UNLINKED_SET",
+        # zvol:
+        "DMU_OT_ZVOL", "DMU_OT_ZVOL_PROP",
+        # other; for testing only!
+        "DMU_OT_PLAIN_OTHER", "DMU_OT_UINT64_OTHER", "DMU_OT_ZAP_OTHER",
+        # new object types:
+        "DMU_OT_ERROR_LOG", "DMU_OT_SPA_HISTORY",
+        "DMU_OT_SPA_HISTORY_OFFSETS", "DMU_OT_POOL_PROPS",
+        "DMU_OT_DSL_PERMS", "DMU_OT_ACL", "DMU_OT_SYSACL",
+        "DMU_OT_FUID", "DMU_OT_FUID_SIZE", "DMU_OT_NEXT_CLONES",
+        "DMU_OT_SCAN_QUEUE", "DMU_OT_USERGROUP_USED",
+        "DMU_OT_USERGROUP_QUOTA", "DMU_OT_USERREFS", "DMU_OT_DDT_ZAP",
+        "DMU_OT_DDT_STATS", "DMU_OT_SA", "DMU_OT_SA_MASTER_NODE",
+        "DMU_OT_SA_ATTR_REGISTRATION", "DMU_OT_SA_ATTR_LAYOUTS",
+        "DMU_OT_SCAN_XLATE", "DMU_OT_DEDUP", "DMU_OT_DEADLIST",
+        "DMU_OT_DEADLIST_HDR", "DMU_OT_DSL_CLONES",
+        "DMU_OT_BPOBJ_SUBOBJ"]
+
+    # If "-rr" option is used, don't convert to string representation
+    if raw > 1:
+        return "%i" % t
+
+    try:
+        return type_strings[t];
+    except IndexError:
+        return "%i" % t
+
+def get_compstring(c):
+    comp_strings = ["ZIO_COMPRESS_INHERIT", "ZIO_COMPRESS_ON",
+                    "ZIO_COMPRESS_OFF",     "ZIO_COMPRESS_LZJB",
+                    "ZIO_COMPRESS_EMPTY",   "ZIO_COMPRESS_GZIP_1",
+                    "ZIO_COMPRESS_GZIP_2",  "ZIO_COMPRESS_GZIP_3",
+                    "ZIO_COMPRESS_GZIP_4",  "ZIO_COMPRESS_GZIP_5",
+                    "ZIO_COMPRESS_GZIP_6",  "ZIO_COMPRESS_GZIP_7",
+                    "ZIO_COMPRESS_GZIP_8",  "ZIO_COMPRESS_GZIP_9",
+                    "ZIO_COMPRESS_ZLE",     "ZIO_COMPRESS_LZ4",
+                    "ZIO_COMPRESS_FUNCTION"]
+
+    # If "-rr" option is used, don't convert to string representation
+    if raw > 1:
+        return "%i" % c
+
+    try:
+        return comp_strings[c];
+    except IndexError:
+        return "%i" % c
+
+def parse_line(line, labels):
+    global hdr
+
+    new = dict()
+    val = None
+    for col in hdr:
+        # These are "special" fields computed in the update_dict
+        # function, prevent KeyError exception on labels[col] for these.
+        if col not in ['bonus', 'cached', 'direct', 'indirect', 'spill']:
+            val = line[labels[col]]
+
+        if col in ['pool', 'flags']:
+            new[col] = str(val)
+        elif col in ['dtype', 'btype']:
+            new[col] = get_typestring(int(val))
+        elif col in ['l2_comp']:
+            new[col] = get_compstring(int(val))
+        else:
+            new[col] = int(val)
+
+    return new
+
+def update_dict(d, k, line, labels):
+    pool   = line[labels['pool']]
+    objset = line[labels['objset']]
+    key    = line[labels[k]]
+
+    dbsize = int(line[labels['dbsize']])
+    blkid  = int(line[labels['blkid']])
+    level  = int(line[labels['level']])
+
+    if pool not in d:
+        d[pool] = dict()
+
+    if objset not in d[pool]:
+        d[pool][objset] = dict()
+
+    if key not in d[pool][objset]:
+        d[pool][objset][key]             = parse_line(line, labels)
+        d[pool][objset][key]['bonus']    = 0
+        d[pool][objset][key]['cached']   = 0
+        d[pool][objset][key]['direct']   = 0
+        d[pool][objset][key]['indirect'] = 0
+        d[pool][objset][key]['spill']    = 0
+
+    d[pool][objset][key]['cached'] += dbsize
+
+    if blkid == -1:
+        d[pool][objset][key]['bonus'] += dbsize
+    elif blkid == -2:
+        d[pool][objset][key]['spill'] += dbsize
+    else:
+        if level == 0:
+            d[pool][objset][key]['direct'] += dbsize
+        else:
+            d[pool][objset][key]['indirect'] += dbsize
+
+    return d
+
+def print_dict(d):
+    print_header()
+    for pool in d.iterkeys():
+        for objset in d[pool].iterkeys():
+            for v in d[pool][objset].itervalues():
+                print_values(v)
+
+def dnodes_build_dict(filehandle):
+    labels = dict()
+    dnodes = dict()
+
+    # First 3 lines are header information, skip the first two
+    for i in range(0, 2):
+        next(filehandle)
+
+    # The third line contains the labels and index locations
+    for i, v in enumerate(next(filehandle).split()):
+        labels[v] = i
+
+    # The rest of the file is buffer information
+    for line in filehandle:
+        update_dict(dnodes, 'object', line.split(), labels)
+
+    return dnodes
+
+def types_build_dict(filehandle):
+    labels = dict()
+    types = dict()
+
+    # First 3 lines are header information, skip the first two
+    for i in range(0, 2):
+        next(filehandle)
+
+    # The third line contains the labels and index locations
+    for i, v in enumerate(next(filehandle).split()):
+        labels[v] = i
+
+    # The rest of the file is buffer information
+    for line in filehandle:
+        update_dict(types, 'dtype', line.split(), labels)
+
+    return types
+
+def buffers_print_all(filehandle):
+    labels = dict()
+
+    # First 3 lines are header information, skip the first two
+    for i in range(0, 2):
+        next(filehandle)
+
+    # The third line contains the labels and index locations
+    for i, v in enumerate(next(filehandle).split()):
+        labels[v] = i
+
+    print_header()
+
+    # The rest of the file is buffer information
+    for line in filehandle:
+        print_values(parse_line(line.split(), labels))
+
+def main():
+    global hdr
+    global sep
+    global raw
+
+    desired_cols = None
+    bflag = False
+    dflag = False
+    hflag = False
+    ifile = None
+    ofile = None
+    tflag = False
+    vflag = False
+    xflag = False
+
+    try:
+        opts, args = getopt.getopt(
+            sys.argv[1:],
+            "bdf:hi:o:rs:tvx",
+            [
+                "buffers",
+                "dnodes",
+                "columns",
+                "help",
+                "infile",
+                "outfile",
+                "seperator",
+                "types",
+                "verbose",
+                "extended"
+            ]
+        )
+    except getopt.error:
+        usage()
+
+    for opt, arg in opts:
+        if opt in ('-b', '--buffers'):
+            bflag = True
+        if opt in ('-d', '--dnodes'):
+            dflag = True
+        if opt in ('-f', '--columns'):
+            desired_cols = arg
+        if opt in ('-h', '--help'):
+            hflag = True
+        if opt in ('-i', '--infile'):
+            ifile = arg
+        if opt in ('-o', '--outfile'):
+            ofile = arg
+        if opt in ('-r', '--raw'):
+            raw += 1
+        if opt in ('-s', '--seperator'):
+            sep = arg
+        if opt in ('-t', '--types'):
+            tflag = True
+        if opt in ('-v', '--verbose'):
+            vflag = True
+        if opt in ('-x', '--extended'):
+            xflag = True
+
+    if hflag or (xflag and desired_cols):
+        usage()
+
+    if vflag:
+        detailed_usage()
+
+    # Ensure at most only one of b, d, or t flags are set
+    if (bflag and dflag) or (bflag and tflag) or (dflag and tflag):
+        usage()
+
+    if bflag:
+        hdr  = bxhdr if xflag else bhdr
+    elif tflag:
+        hdr  = txhdr if xflag else thdr
+    else: # Even if dflag is False, it's the default if none set
+        dflag = True
+        hdr = dxhdr if xflag else dhdr
+
+    if desired_cols:
+        hdr = desired_cols.split(",")
+
+        invalid = []
+        incompat = []
+        for ele in hdr:
+            if ele not in cols:
+                invalid.append(ele)
+            elif ((bflag and bincompat and ele in bincompat) or
+                  (dflag and dincompat and ele in dincompat) or
+                  (tflag and tincompat and ele in tincompat)):
+                    incompat.append(ele)
+
+        if len(invalid) > 0:
+            sys.stderr.write("Invalid column definition! -- %s\n" % invalid)
+            usage()
+
+        if len(incompat) > 0:
+            sys.stderr.write("Incompatible field specified! -- %s\n" % incompat)
+            usage()
+
+    if ofile:
+        try:
+            tmp = open(ofile, "w")
+            sys.stdout = tmp
+
+        except:
+            sys.stderr.write("Cannot open %s for writing\n", ofile)
+            sys.exit(1)
+
+    if not ifile:
+        ifile = '/proc/spl/kstat/zfs/dbufs'
+
+    if ifile is not "-":
+        try:
+            tmp = open(ifile, "r")
+            sys.stdin = tmp
+        except:
+            sys.stderr.write("Cannot open %s for reading\n" % ifile)
+            sys.exit(1)
+
+    if bflag:
+        buffers_print_all(sys.stdin)
+
+    if dflag:
+        print_dict(dnodes_build_dict(sys.stdin))
+
+    if tflag:
+        print_dict(types_build_dict(sys.stdin))
+
+if __name__ == '__main__':
+    main()
diff --git a/configure.ac b/configure.ac
index 08b807e3f..7c4809426 100644
--- a/configure.ac
+++ b/configure.ac
@@ -104,6 +104,7 @@ AC_CONFIG_FILES([
 	cmd/zvol_id/Makefile
 	cmd/vdev_id/Makefile
 	cmd/arcstat/Makefile
+	cmd/dbufstat/Makefile
 	module/Makefile
 	module/avl/Makefile
 	module/nvpair/Makefile
diff --git a/include/sys/arc.h b/include/sys/arc.h
index 8c10d947c..efafb551a 100644
--- a/include/sys/arc.h
+++ b/include/sys/arc.h
@@ -92,6 +92,36 @@ typedef enum arc_space_type {
 	ARC_SPACE_NUMTYPES
 } arc_space_type_t;
 
+typedef enum arc_state_type {
+	ARC_STATE_ANON,
+	ARC_STATE_MRU,
+	ARC_STATE_MRU_GHOST,
+	ARC_STATE_MFU,
+	ARC_STATE_MFU_GHOST,
+	ARC_STATE_L2C_ONLY,
+	ARC_STATE_NUMTYPES
+} arc_state_type_t;
+
+typedef struct arc_buf_info {
+	arc_state_type_t	abi_state_type;
+	arc_buf_contents_t	abi_state_contents;
+	uint64_t		abi_state_index;
+	uint32_t		abi_flags;
+	uint32_t		abi_datacnt;
+	uint64_t		abi_size;
+	uint64_t		abi_spa;
+	uint64_t		abi_access;
+	uint32_t		abi_mru_hits;
+	uint32_t		abi_mru_ghost_hits;
+	uint32_t		abi_mfu_hits;
+	uint32_t		abi_mfu_ghost_hits;
+	uint32_t		abi_l2arc_hits;
+	uint32_t		abi_holds;
+	uint64_t		abi_l2arc_dattr;
+	uint64_t		abi_l2arc_asize;
+	enum zio_compress	abi_l2arc_compress;
+} arc_buf_info_t;
+
 void arc_space_consume(uint64_t space, arc_space_type_t type);
 void arc_space_return(uint64_t space, arc_space_type_t type);
 arc_buf_t *arc_buf_alloc(spa_t *spa, int size, void *tag,
@@ -101,6 +131,7 @@ void arc_return_buf(arc_buf_t *buf, void *tag);
 void arc_loan_inuse_buf(arc_buf_t *buf, void *tag);
 void arc_buf_add_ref(arc_buf_t *buf, void *tag);
 boolean_t arc_buf_remove_ref(arc_buf_t *buf, void *tag);
+void arc_buf_info(arc_buf_t *buf, arc_buf_info_t *abi, int state_index);
 int arc_buf_size(arc_buf_t *buf);
 void arc_release(arc_buf_t *buf, void *tag);
 int arc_released(arc_buf_t *buf);
diff --git a/include/sys/dbuf.h b/include/sys/dbuf.h
index 8cd1fde01..85e967d0f 100644
--- a/include/sys/dbuf.h
+++ b/include/sys/dbuf.h
@@ -282,6 +282,9 @@ void dbuf_free_range(struct dnode *dn, uint64_t start, uint64_t end,
 
 void dbuf_new_size(dmu_buf_impl_t *db, int size, dmu_tx_t *tx);
 
+void dbuf_stats_init(dbuf_hash_table_t *hash);
+void dbuf_stats_destroy(void);
+
 #define	DB_DNODE(_db)		((_db)->db_dnode_handle->dnh_dnode)
 #define	DB_DNODE_LOCK(_db)	((_db)->db_dnode_handle->dnh_zrlock)
 #define	DB_DNODE_ENTER(_db)	(zrl_add(&DB_DNODE_LOCK(_db)))
diff --git a/include/sys/dmu.h b/include/sys/dmu.h
index b0db7604d..fd1460d5c 100644
--- a/include/sys/dmu.h
+++ b/include/sys/dmu.h
@@ -660,6 +660,7 @@ extern const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS];
  * If doi is NULL, just indicates whether the object exists.
  */
 int dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi);
+void __dmu_object_info_from_dnode(struct dnode *dn, dmu_object_info_t *doi);
 void dmu_object_info_from_dnode(struct dnode *dn, dmu_object_info_t *doi);
 void dmu_object_info_from_db(dmu_buf_t *db, dmu_object_info_t *doi);
 void dmu_object_size_from_db(dmu_buf_t *db, uint32_t *blksize,
diff --git a/include/sys/dsl_pool.h b/include/sys/dsl_pool.h
index 51b588e6a..25abd9c03 100644
--- a/include/sys/dsl_pool.h
+++ b/include/sys/dsl_pool.h
@@ -71,13 +71,6 @@ typedef struct zfs_all_blkstats {
 	zfs_blkstat_t	zab_type[DN_MAX_LEVELS + 1][DMU_OT_TOTAL + 1];
 } zfs_all_blkstats_t;
 
-typedef struct txg_history {
-	kstat_txg_t	th_kstat;
-	vdev_stat_t	th_vs1;
-	vdev_stat_t	th_vs2;
-	kmutex_t	th_lock;
-	list_node_t	th_link;
-} txg_history_t;
 
 typedef struct dsl_pool {
 	/* Immutable */
@@ -89,8 +82,6 @@ typedef struct dsl_pool {
 	struct dsl_dataset *dp_origin_snap;
 	uint64_t dp_root_dir_obj;
 	struct taskq *dp_iput_taskq;
-	kstat_t *dp_txg_kstat;
-	kstat_t *dp_tx_assign_kstat;
 
 	/* No lock needed - sync context only */
 	blkptr_t dp_meta_rootbp;
@@ -111,11 +102,6 @@ typedef struct dsl_pool {
 	uint64_t dp_mos_used_delta;
 	uint64_t dp_mos_compressed_delta;
 	uint64_t dp_mos_uncompressed_delta;
-	uint64_t dp_txg_history_size;
-	list_t dp_txg_history;
-	uint64_t dp_tx_assign_size;
-	kstat_named_t *dp_tx_assign_buckets;
-
 
 	/* Has its own locking */
 	tx_state_t dp_tx;
@@ -171,12 +157,6 @@ int dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **);
 int dsl_pool_hold(const char *name, void *tag, dsl_pool_t **dp);
 void dsl_pool_rele(dsl_pool_t *dp, void *tag);
 
-void dsl_pool_tx_assign_add_usecs(dsl_pool_t *dp, uint64_t usecs);
-
-txg_history_t *dsl_pool_txg_history_add(dsl_pool_t *dp, uint64_t txg);
-txg_history_t *dsl_pool_txg_history_get(dsl_pool_t *dp, uint64_t txg);
-void dsl_pool_txg_history_put(txg_history_t *th);
-
 #ifdef	__cplusplus
 }
 #endif
diff --git a/include/sys/spa.h b/include/sys/spa.h
index 401ae8343..cb3ce11bc 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -51,6 +51,8 @@ typedef struct zilog zilog_t;
 typedef struct spa_aux_vdev spa_aux_vdev_t;
 typedef struct ddt ddt_t;
 typedef struct ddt_entry ddt_entry_t;
+typedef struct zbookmark zbookmark_t;
+
 struct dsl_pool;
 struct dsl_dataset;
 
@@ -534,6 +536,41 @@ extern boolean_t spa_refcount_zero(spa_t *spa);
 #define	SCL_ALL		((1 << SCL_LOCKS) - 1)
 #define	SCL_STATE_ALL	(SCL_STATE | SCL_L2ARC | SCL_ZIO)
 
+/* Historical pool statistics */
+typedef struct spa_stats_history {
+	kmutex_t		lock;
+	uint64_t		count;
+	uint64_t		size;
+	kstat_t			*kstat;
+	void			*private;
+	list_t			list;
+} spa_stats_history_t;
+
+typedef struct spa_stats {
+	spa_stats_history_t	read_history;
+	spa_stats_history_t	txg_history;
+	spa_stats_history_t	tx_assign_histogram;
+} spa_stats_t;
+
+typedef enum txg_state {
+	TXG_STATE_BIRTH		= 0,
+	TXG_STATE_OPEN		= 1,
+	TXG_STATE_QUIESCED	= 2,
+	TXG_STATE_SYNCED	= 3,
+	TXG_STATE_COMMITTED	= 4,
+} txg_state_t;
+
+extern void spa_stats_init(spa_t *spa);
+extern void spa_stats_destroy(spa_t *spa);
+extern void spa_read_history_add(spa_t *spa, const zbookmark_t *zb,
+    uint32_t aflags);
+extern void spa_txg_history_add(spa_t *spa, uint64_t txg);
+extern int spa_txg_history_set(spa_t *spa,  uint64_t txg,
+    txg_state_t completed_state, hrtime_t completed_time);
+extern int spa_txg_history_set_io(spa_t *spa,  uint64_t txg, uint64_t nread,
+    uint64_t nwritten, uint64_t reads, uint64_t writes, uint64_t nreserved);
+extern void spa_tx_assign_add_nsecs(spa_t *spa, uint64_t nsecs);
+
 /* Pool configuration locks */
 extern int spa_config_tryenter(spa_t *spa, int locks, void *tag, krw_t rw);
 extern void spa_config_enter(spa_t *spa, int locks, void *tag, krw_t rw);
diff --git a/include/sys/spa_impl.h b/include/sys/spa_impl.h
index 47dfe432e..107d14a76 100644
--- a/include/sys/spa_impl.h
+++ b/include/sys/spa_impl.h
@@ -236,6 +236,8 @@ struct spa {
 	uint64_t	spa_deadman_calls;	/* number of deadman calls */
 	uint64_t	spa_sync_starttime;	/* starting time fo spa_sync */
 	uint64_t	spa_deadman_synctime;	/* deadman expiration timer */
+	spa_stats_t	spa_stats;		/* assorted spa statistics */
+
 	/*
 	 * spa_refcnt & spa_config_lock must be the last elements
 	 * because refcount_t changes size based on compilation options.
diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index a126c058e..dfd11d9f1 100644
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -210,6 +210,7 @@ typedef struct kthread {
 } kthread_t;
 
 #define	curthread			zk_thread_current()
+#define	getcomm()			"unknown"
 #define	thread_exit			zk_thread_exit
 #define	thread_create(stk, stksize, func, arg, len, pp, state, pri)	\
 	zk_thread_create(stk, stksize, (thread_func_t)func, arg,	\
@@ -347,6 +348,10 @@ extern kstat_t *kstat_create(char *, int,
     char *, char *, uchar_t, ulong_t, uchar_t);
 extern void kstat_install(kstat_t *);
 extern void kstat_delete(kstat_t *);
+extern void kstat_set_raw_ops(kstat_t *ksp,
+    int (*headers)(char *buf, size_t size),
+    int (*data)(char *buf, size_t size, void *data),
+    void *(*addr)(kstat_t *ksp, loff_t index));
 
 /*
  * Kernel memory
diff --git a/include/sys/zio.h b/include/sys/zio.h
index 189966bef..f5a128e0b 100644
--- a/include/sys/zio.h
+++ b/include/sys/zio.h
@@ -256,12 +256,13 @@ extern char *zio_type_name[ZIO_TYPES];
  * Therefore it must not change size or alignment between 32/64 bit
  * compilation options.
  */
-typedef struct zbookmark {
+struct zbookmark {
 	uint64_t	zb_objset;
 	uint64_t	zb_object;
 	int64_t		zb_level;
 	uint64_t	zb_blkid;
-} zbookmark_t;
+	char *		zb_func;
+};
 
 #define	SET_BOOKMARK(zb, objset, object, level, blkid)  \
 {                                                       \
@@ -269,6 +270,7 @@ typedef struct zbookmark {
 	(zb)->zb_object = object;                       \
 	(zb)->zb_level = level;                         \
 	(zb)->zb_blkid = blkid;                         \
+	(zb)->zb_func = FTAG;                           \
 }
 
 #define	ZB_DESTROYED_OBJSET	(-1ULL)
diff --git a/lib/libspl/include/sys/kstat.h b/lib/libspl/include/sys/kstat.h
index 6bd2ec878..fcd3ed98b 100644
--- a/lib/libspl/include/sys/kstat.h
+++ b/lib/libspl/include/sys/kstat.h
@@ -228,10 +228,8 @@ typedef struct kstat32 {
 					/* ks_ndata == 1 */
 #define	KSTAT_TYPE_TIMER	4	/* event timer */
 					/* ks_ndata >= 1 */
-#define	KSTAT_TYPE_TXG		5	/* txg statistics */
-					/* ks_ndata >= 0 */
 
-#define	KSTAT_NUM_TYPES		6
+#define	KSTAT_NUM_TYPES		5
 
 /*
  * kstat class
@@ -700,29 +698,6 @@ typedef struct kstat_timer {
 
 #define	KSTAT_TIMER_PTR(kptr)	((kstat_timer_t *)(kptr)->ks_data)
 
-/*
- * TXG statistics - bytes read/written and iops performed
- */
-typedef enum kstat_txg_state {
-	TXG_STATE_OPEN      = 1,
-	TXG_STATE_QUIESCING = 2,
-	TXG_STATE_SYNCING   = 3,
-	TXG_STATE_COMMITTED = 4,
-} kstat_txg_state_t;
-
-typedef struct kstat_txg {
-	u_longlong_t		txg;		/* txg id */
-	kstat_txg_state_t	state;		/* txg state */
-	hrtime_t		birth;		/* birth time stamp */
-	u_longlong_t		nread;		/* number of bytes read */
-	u_longlong_t		nwritten;	/* number of bytes written */
-	uint_t			reads;		/* number of read operations */
-	uint_t			writes;		/* number of write operations */
-	hrtime_t		open_time;	/* open time */
-	hrtime_t		quiesce_time;	/* quiesce time */
-	hrtime_t		sync_time;	/* sync time */
-} kstat_txg_t;
-
 #if	defined(_KERNEL)
 
 #include <sys/t_lock.h>
diff --git a/lib/libzpool/Makefile.am b/lib/libzpool/Makefile.am
index da81659d2..e4189a378 100644
--- a/lib/libzpool/Makefile.am
+++ b/lib/libzpool/Makefile.am
@@ -25,6 +25,7 @@ libzpool_la_SOURCES = \
 	$(top_srcdir)/module/zfs/bpobj.c \
 	$(top_srcdir)/module/zfs/bptree.c \
 	$(top_srcdir)/module/zfs/dbuf.c \
+	$(top_srcdir)/module/zfs/dbuf_stats.c \
 	$(top_srcdir)/module/zfs/ddt.c \
 	$(top_srcdir)/module/zfs/ddt_zap.c \
 	$(top_srcdir)/module/zfs/dmu.c \
@@ -62,6 +63,7 @@ libzpool_la_SOURCES = \
 	$(top_srcdir)/module/zfs/spa_errlog.c \
 	$(top_srcdir)/module/zfs/spa_history.c \
 	$(top_srcdir)/module/zfs/spa_misc.c \
+	$(top_srcdir)/module/zfs/spa_stats.c \
 	$(top_srcdir)/module/zfs/space_map.c \
 	$(top_srcdir)/module/zfs/txg.c \
 	$(top_srcdir)/module/zfs/uberblock.c \
diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index e4d645cf7..57a3739e2 100644
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -240,6 +240,14 @@ void
 kstat_delete(kstat_t *ksp)
 {}
 
+/*ARGSUSED*/
+void
+kstat_set_raw_ops(kstat_t *ksp,
+    int (*headers)(char *buf, size_t size),
+    int (*data)(char *buf, size_t size, void *data),
+    void *(*addr)(kstat_t *ksp, loff_t index))
+{}
+
 /*
  * =========================================================================
  * mutexes
diff --git a/module/zfs/Makefile.in b/module/zfs/Makefile.in
index e71228454..5552436ad 100644
--- a/module/zfs/Makefile.in
+++ b/module/zfs/Makefile.in
@@ -8,6 +8,7 @@ $(MODULE)-objs += @top_srcdir@/module/zfs/arc.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/bplist.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/bpobj.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/dbuf.o
+$(MODULE)-objs += @top_srcdir@/module/zfs/dbuf_stats.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/bptree.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/ddt.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/ddt_zap.o
@@ -44,6 +45,7 @@ $(MODULE)-objs += @top_srcdir@/module/zfs/spa_config.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/spa_errlog.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/spa_history.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/spa_misc.o
+$(MODULE)-objs += @top_srcdir@/module/zfs/spa_stats.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/space_map.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/txg.o
 $(MODULE)-objs += @top_srcdir@/module/zfs/uberblock.o
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 1298c5b91..9098988fd 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -232,6 +232,7 @@ typedef struct arc_state {
 	uint64_t arcs_lsize[ARC_BUFC_NUMTYPES];	/* amount of evictable data */
 	uint64_t arcs_size;	/* total amount of data in this state */
 	kmutex_t arcs_mtx;
+	arc_state_type_t arcs_state;
 } arc_state_t;
 
 /* The 6 states: */
@@ -534,6 +535,11 @@ struct arc_buf_hdr {
 
 	/* updated atomically */
 	clock_t			b_arc_access;
+	uint32_t		b_mru_hits;
+	uint32_t		b_mru_ghost_hits;
+	uint32_t		b_mfu_hits;
+	uint32_t		b_mfu_ghost_hits;
+	uint32_t		b_l2_hits;
 
 	/* self protecting */
 	refcount_t		b_refcnt;
@@ -709,7 +715,8 @@ struct l2arc_buf_hdr {
 	/* compression applied to buffer data */
 	enum zio_compress	b_compress;
 	/* real alloc'd buffer size depending on b_compress applied */
-	int			b_asize;
+	uint32_t		b_asize;
+	uint32_t		b_hits;
 	/* temporary buffer holder for in-flight compressed data */
 	void			*b_tmp_cdata;
 };
@@ -1138,6 +1145,54 @@ remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
 }
 
 /*
+ * Returns detailed information about a specific arc buffer.  When the
+ * state_index argument is set the function will calculate the arc header
+ * list position for its arc state.  Since this requires a linear traversal
+ * callers are strongly encourage not to do this.  However, it can be helpful
+ * for targeted analysis so the functionality is provided.
+ */
+void
+arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index)
+{
+	arc_buf_hdr_t *hdr = ab->b_hdr;
+	arc_state_t *state = hdr->b_state;
+
+	memset(abi, 0, sizeof(arc_buf_info_t));
+	abi->abi_flags = hdr->b_flags;
+	abi->abi_datacnt = hdr->b_datacnt;
+	abi->abi_state_type = state ? state->arcs_state : ARC_STATE_ANON;
+	abi->abi_state_contents = hdr->b_type;
+	abi->abi_state_index = -1;
+	abi->abi_size = hdr->b_size;
+	abi->abi_access = hdr->b_arc_access;
+	abi->abi_mru_hits = hdr->b_mru_hits;
+	abi->abi_mru_ghost_hits = hdr->b_mru_ghost_hits;
+	abi->abi_mfu_hits = hdr->b_mfu_hits;
+	abi->abi_mfu_ghost_hits = hdr->b_mfu_ghost_hits;
+	abi->abi_holds = refcount_count(&hdr->b_refcnt);
+
+	if (hdr->b_l2hdr) {
+		abi->abi_l2arc_dattr = hdr->b_l2hdr->b_daddr;
+		abi->abi_l2arc_asize = hdr->b_l2hdr->b_asize;
+		abi->abi_l2arc_compress = hdr->b_l2hdr->b_compress;
+		abi->abi_l2arc_hits = hdr->b_l2hdr->b_hits;
+	}
+
+	if (state && state_index && list_link_active(&hdr->b_arc_node)) {
+		list_t *list = &state->arcs_list[hdr->b_type];
+		arc_buf_hdr_t *h;
+
+		mutex_enter(&state->arcs_mtx);
+		for (h = list_head(list); h != NULL; h = list_next(list, h)) {
+			abi->abi_state_index++;
+			if (h == hdr)
+				break;
+		}
+		mutex_exit(&state->arcs_mtx);
+	}
+}
+
+/*
  * Move the supplied buffer to the indicated state.  The mutex
  * for the buffer must be held by the caller.
  */
@@ -1298,6 +1353,11 @@ arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
 	hdr->b_spa = spa_load_guid(spa);
 	hdr->b_state = arc_anon;
 	hdr->b_arc_access = 0;
+	hdr->b_mru_hits = 0;
+	hdr->b_mru_ghost_hits = 0;
+	hdr->b_mfu_hits = 0;
+	hdr->b_mfu_ghost_hits = 0;
+	hdr->b_l2_hits = 0;
 	buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
 	buf->b_hdr = hdr;
 	buf->b_data = NULL;
@@ -2670,6 +2730,7 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 				ASSERT(list_link_active(&buf->b_arc_node));
 			} else {
 				buf->b_flags &= ~ARC_PREFETCH;
+				atomic_inc_32(&buf->b_mru_hits);
 				ARCSTAT_BUMP(arcstat_mru_hits);
 			}
 			buf->b_arc_access = now;
@@ -2691,6 +2752,7 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 			DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
 			arc_change_state(arc_mfu, buf, hash_lock);
 		}
+		atomic_inc_32(&buf->b_mru_hits);
 		ARCSTAT_BUMP(arcstat_mru_hits);
 	} else if (buf->b_state == arc_mru_ghost) {
 		arc_state_t	*new_state;
@@ -2713,6 +2775,7 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 		buf->b_arc_access = ddi_get_lbolt();
 		arc_change_state(new_state, buf, hash_lock);
 
+		atomic_inc_32(&buf->b_mru_ghost_hits);
 		ARCSTAT_BUMP(arcstat_mru_ghost_hits);
 	} else if (buf->b_state == arc_mfu) {
 		/*
@@ -2728,6 +2791,7 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 			ASSERT(refcount_count(&buf->b_refcnt) == 0);
 			ASSERT(list_link_active(&buf->b_arc_node));
 		}
+		atomic_inc_32(&buf->b_mfu_hits);
 		ARCSTAT_BUMP(arcstat_mfu_hits);
 		buf->b_arc_access = ddi_get_lbolt();
 	} else if (buf->b_state == arc_mfu_ghost) {
@@ -2751,6 +2815,7 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 		DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
 		arc_change_state(new_state, buf, hash_lock);
 
+		atomic_inc_32(&buf->b_mfu_ghost_hits);
 		ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
 	} else if (buf->b_state == arc_l2c_only) {
 		/*
@@ -2943,6 +3008,7 @@ arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
 	kmutex_t *hash_lock;
 	zio_t *rzio;
 	uint64_t guid = spa_load_guid(spa);
+	int rc = 0;
 
 top:
 	hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
@@ -2976,10 +3042,10 @@ top:
 				hdr->b_acb = acb;
 				add_reference(hdr, hash_lock, private);
 				mutex_exit(hash_lock);
-				return (0);
+				goto out;
 			}
 			mutex_exit(hash_lock);
-			return (0);
+			goto out;
 		}
 
 		ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
@@ -3133,6 +3199,7 @@ top:
 
 				DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
 				ARCSTAT_BUMP(arcstat_l2_hits);
+				atomic_inc_32(&hdr->b_l2hdr->b_hits);
 
 				cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
 				    KM_PUSHPAGE);
@@ -3174,12 +3241,12 @@ top:
 
 				if (*arc_flags & ARC_NOWAIT) {
 					zio_nowait(rzio);
-					return (0);
+					goto out;
 				}
 
 				ASSERT(*arc_flags & ARC_WAIT);
 				if (zio_wait(rzio) == 0)
-					return (0);
+					goto out;
 
 				/* l2arc read error; goto zio_read() */
 			} else {
@@ -3203,13 +3270,18 @@ top:
 		rzio = zio_read(pio, spa, bp, buf->b_data, size,
 		    arc_read_done, buf, priority, zio_flags, zb);
 
-		if (*arc_flags & ARC_WAIT)
-			return (zio_wait(rzio));
+		if (*arc_flags & ARC_WAIT) {
+			rc = zio_wait(rzio);
+			goto out;
+		}
 
 		ASSERT(*arc_flags & ARC_NOWAIT);
 		zio_nowait(rzio);
 	}
-	return (0);
+
+out:
+	spa_read_history_add(spa, zb, *arc_flags);
+	return (rc);
 }
 
 arc_prune_t *
@@ -3463,6 +3535,11 @@ arc_release(arc_buf_t *buf, void *tag)
 		nhdr->b_buf = buf;
 		nhdr->b_state = arc_anon;
 		nhdr->b_arc_access = 0;
+		nhdr->b_mru_hits = 0;
+		nhdr->b_mru_ghost_hits = 0;
+		nhdr->b_mfu_hits = 0;
+		nhdr->b_mfu_ghost_hits = 0;
+		nhdr->b_l2_hits = 0;
 		nhdr->b_flags = flags & ARC_L2_WRITING;
 		nhdr->b_l2hdr = NULL;
 		nhdr->b_datacnt = 1;
@@ -3479,6 +3556,11 @@ arc_release(arc_buf_t *buf, void *tag)
 		if (hdr->b_state != arc_anon)
 			arc_change_state(arc_anon, hdr, hash_lock);
 		hdr->b_arc_access = 0;
+		hdr->b_mru_hits = 0;
+		hdr->b_mru_ghost_hits = 0;
+		hdr->b_mfu_hits = 0;
+		hdr->b_mfu_ghost_hits = 0;
+		hdr->b_l2_hits = 0;
 		if (hash_lock)
 			mutex_exit(hash_lock);
 
@@ -3896,6 +3978,13 @@ arc_init(void)
 	list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
 	    sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
 
+	arc_anon->arcs_state = ARC_STATE_ANON;
+	arc_mru->arcs_state = ARC_STATE_MRU;
+	arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST;
+	arc_mfu->arcs_state = ARC_STATE_MFU;
+	arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST;
+	arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY;
+
 	buf_init();
 
 	arc_thread_exit = 0;
@@ -4779,6 +4868,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
 			l2hdr->b_compress = ZIO_COMPRESS_OFF;
 			l2hdr->b_asize = ab->b_size;
 			l2hdr->b_tmp_cdata = ab->b_buf->b_data;
+			l2hdr->b_hits = 0;
 
 			buf_sz = ab->b_size;
 			ab->b_l2hdr = l2hdr;
@@ -5311,6 +5401,7 @@ l2arc_stop(void)
 #if defined(_KERNEL) && defined(HAVE_SPL)
 EXPORT_SYMBOL(arc_read);
 EXPORT_SYMBOL(arc_buf_remove_ref);
+EXPORT_SYMBOL(arc_buf_info);
 EXPORT_SYMBOL(arc_getbuf_func);
 EXPORT_SYMBOL(arc_add_prune_callback);
 EXPORT_SYMBOL(arc_remove_prune_callback);
diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index d655d6621..44e9419b7 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -317,6 +317,8 @@ retry:
 
 	for (i = 0; i < DBUF_MUTEXES; i++)
 		mutex_init(&h->hash_mutexes[i], NULL, MUTEX_DEFAULT, NULL);
+
+	dbuf_stats_init(h);
 }
 
 void
@@ -325,6 +327,8 @@ dbuf_fini(void)
 	dbuf_hash_table_t *h = &dbuf_hash_table;
 	int i;
 
+	dbuf_stats_destroy();
+
 	for (i = 0; i < DBUF_MUTEXES; i++)
 		mutex_destroy(&h->hash_mutexes[i]);
 #if defined(_KERNEL) && defined(HAVE_SPL)
diff --git a/module/zfs/dbuf_stats.c b/module/zfs/dbuf_stats.c
new file mode 100644
index 000000000..ef760eaba
--- /dev/null
+++ b/module/zfs/dbuf_stats.c
@@ -0,0 +1,230 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/dbuf.h>
+#include <sys/dmu_objset.h>
+
+/*
+ * Calculate the index of the arc header for the state, disabled by default.
+ */
+int zfs_dbuf_state_index = 0;
+
+/*
+ * ==========================================================================
+ * Dbuf Hash Read Routines
+ * ==========================================================================
+ */
+typedef struct dbuf_stats_t {
+	kmutex_t		lock;
+	kstat_t			*kstat;
+	dbuf_hash_table_t	*hash;
+	int			idx;
+} dbuf_stats_t;
+
+static dbuf_stats_t dbuf_stats_hash_table;
+
+static int
+dbuf_stats_hash_table_headers(char *buf, size_t size)
+{
+	size = snprintf(buf, size - 1,
+	    "%-88s | %-124s | %s\n"
+	    "%-16s %-8s %-8s %-8s %-8s %-8s %-8s %-5s %-5s %5s | "
+	    "%-5s %-5s %-6s %-8s %-6s %-8s %-12s "
+	    "%-6s %-6s %-6s %-6s %-6s %-8s %-8s %-8s %-5s | "
+	    "%-6s %-6s %-8s %-8s %-6s %-6s %-5s %-8s %-8s\n",
+	    "dbuf", "arcbuf", "dnode", "pool", "objset", "object", "level",
+	    "blkid", "offset", "dbsize", "meta", "state", "dbholds", "list",
+	    "atype", "index", "flags", "count", "asize", "access", "mru", "gmru",
+	    "mfu", "gmfu", "l2", "l2_dattr", "l2_asize", "l2_comp", "aholds",
+	    "dtype", "btype", "data_bs", "meta_bs", "bsize",
+	    "lvls", "dholds", "blocks", "dsize");
+        buf[size] = '\0';
+
+	return (0);
+}
+
+int
+__dbuf_stats_hash_table_data(char *buf, size_t size, dmu_buf_impl_t *db)
+{
+	arc_buf_info_t abi = { 0 };
+	dmu_object_info_t doi = { 0 };
+	dnode_t *dn = DB_DNODE(db);
+
+	if (db->db_buf)
+		arc_buf_info(db->db_buf, &abi, zfs_dbuf_state_index);
+
+	if (dn)
+		__dmu_object_info_from_dnode(dn, &doi);
+
+	size = snprintf(buf, size - 1,
+	    "%-16s %-8llu %-8lld %-8lld %-8lld %-8llu %-8llu %-5d %-5d %-5lu | "
+	    "%-5d %-5d %-6lld 0x%-6x %-6lu %-8llu %-12llu "
+	    "%-6lu %-6lu %-6lu %-6lu %-6lu %-8llu %-8llu %-8d %-5lu | "
+	    "%-6d %-6d %-8lu %-8lu %-6llu %-6lu %-5lu %-8llu %-8llu\n",
+	    /* dmu_buf_impl_t */
+	    spa_name(dn->dn_objset->os_spa),
+	    (u_longlong_t)dmu_objset_id(db->db_objset),
+	    (longlong_t)db->db.db_object,
+	    (longlong_t)db->db_level,
+	    (longlong_t)db->db_blkid,
+	    (u_longlong_t)db->db.db_offset,
+	    (u_longlong_t)db->db.db_size,
+	    !!dbuf_is_metadata(db),
+	    db->db_state,
+	    (ulong_t)refcount_count(&db->db_holds),
+	    /* arc_buf_info_t */
+	    abi.abi_state_type,
+	    abi.abi_state_contents,
+	    (longlong_t)abi.abi_state_index,
+	    abi.abi_flags,
+	    (ulong_t)abi.abi_datacnt,
+	    (u_longlong_t)abi.abi_size,
+	    (u_longlong_t)abi.abi_access,
+	    (ulong_t)abi.abi_mru_hits,
+	    (ulong_t)abi.abi_mru_ghost_hits,
+	    (ulong_t)abi.abi_mfu_hits,
+	    (ulong_t)abi.abi_mfu_ghost_hits,
+	    (ulong_t)abi.abi_l2arc_hits,
+	    (u_longlong_t)abi.abi_l2arc_dattr,
+	    (u_longlong_t)abi.abi_l2arc_asize,
+	    abi.abi_l2arc_compress,
+	    (ulong_t)abi.abi_holds,
+	    /* dmu_object_info_t */
+	    doi.doi_type,
+	    doi.doi_bonus_type,
+	    (ulong_t)doi.doi_data_block_size,
+	    (ulong_t)doi.doi_metadata_block_size,
+	    (u_longlong_t)doi.doi_bonus_size,
+	    (ulong_t)doi.doi_indirection,
+	    (ulong_t)refcount_count(&dn->dn_holds),
+	    (u_longlong_t)doi.doi_fill_count,
+	    (u_longlong_t)doi.doi_max_offset);
+        buf[size] = '\0';
+
+	return (size);
+}
+
+static int
+dbuf_stats_hash_table_data(char *buf, size_t size, void *data)
+{
+	dbuf_stats_t *dsh = (dbuf_stats_t *)data;
+	dbuf_hash_table_t *h = dsh->hash;
+	dmu_buf_impl_t *db;
+	int length, error = 0;
+
+	ASSERT3S(dsh->idx, >=, 0);
+	ASSERT3S(dsh->idx, <=, h->hash_table_mask);
+	memset(buf, 0, size);
+
+	mutex_enter(DBUF_HASH_MUTEX(h, dsh->idx));
+	for (db = h->hash_table[dsh->idx]; db != NULL; db = db->db_hash_next) {
+		/*
+		 * Returning ENOMEM will cause the data and header functions
+		 * to be called with a larger scratch buffers.
+		 */
+		if (size < 512) {
+			error = ENOMEM;
+			break;
+		}
+
+		mutex_enter(&db->db_mtx);
+		mutex_exit(DBUF_HASH_MUTEX(h, dsh->idx));
+
+		length = __dbuf_stats_hash_table_data(buf, size, db);
+		buf += length;
+		size -= length;
+
+		mutex_exit(&db->db_mtx);
+		mutex_enter(DBUF_HASH_MUTEX(h, dsh->idx));
+	}
+	mutex_exit(DBUF_HASH_MUTEX(h, dsh->idx));
+
+	return (error);
+}
+
+static void *
+dbuf_stats_hash_table_addr(kstat_t *ksp, loff_t n)
+{
+	dbuf_stats_t *dsh = ksp->ks_private;
+
+        ASSERT(MUTEX_HELD(&dsh->lock));
+
+	if (n <= dsh->hash->hash_table_mask) {
+		dsh->idx = n;
+		return (dsh);
+	}
+
+	return (NULL);
+}
+
+static void
+dbuf_stats_hash_table_init(dbuf_hash_table_t *hash)
+{
+	dbuf_stats_t *dsh = &dbuf_stats_hash_table;
+	kstat_t *ksp;
+
+	mutex_init(&dsh->lock, NULL, MUTEX_DEFAULT, NULL);
+	dsh->hash = hash;
+
+	ksp = kstat_create("zfs", 0, "dbufs", "misc",
+	    KSTAT_TYPE_RAW, 0, KSTAT_FLAG_VIRTUAL);
+	dsh->kstat = ksp;
+
+	if (ksp) {
+		ksp->ks_lock = &dsh->lock;
+		ksp->ks_ndata = UINT32_MAX;
+		ksp->ks_private = dsh;
+		kstat_set_raw_ops(ksp, dbuf_stats_hash_table_headers,
+		    dbuf_stats_hash_table_data, dbuf_stats_hash_table_addr);
+		kstat_install(ksp);
+	}
+}
+
+static void
+dbuf_stats_hash_table_destroy(void)
+{
+	dbuf_stats_t *dsh = &dbuf_stats_hash_table;
+	kstat_t *ksp;
+
+	ksp = dsh->kstat;
+	if (ksp)
+		kstat_delete(ksp);
+
+	mutex_destroy(&dsh->lock);
+}
+
+void
+dbuf_stats_init(dbuf_hash_table_t *hash)
+{
+	dbuf_stats_hash_table_init(hash);
+}
+
+void
+dbuf_stats_destroy(void)
+{
+	dbuf_stats_hash_table_destroy();
+}
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+module_param(zfs_dbuf_state_index, int, 0644);
+MODULE_PARM_DESC(zfs_dbuf_state_index, "Calculate arc header index");
+#endif
diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c
index cbf4790b1..4ec9cb46a 100644
--- a/module/zfs/dmu.c
+++ b/module/zfs/dmu.c
@@ -1815,16 +1815,11 @@ dmu_offset_next(objset_t *os, uint64_t object, boolean_t hole, uint64_t *off)
 }
 
 void
-dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
+__dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
 {
-	dnode_phys_t *dnp;
+	dnode_phys_t *dnp = dn->dn_phys;
 	int i;
 
-	rw_enter(&dn->dn_struct_rwlock, RW_READER);
-	mutex_enter(&dn->dn_mtx);
-
-	dnp = dn->dn_phys;
-
 	doi->doi_data_block_size = dn->dn_datablksz;
 	doi->doi_metadata_block_size = dn->dn_indblkshift ?
 	    1ULL << dn->dn_indblkshift : 0;
@@ -1839,6 +1834,15 @@ dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
 	doi->doi_fill_count = 0;
 	for (i = 0; i < dnp->dn_nblkptr; i++)
 		doi->doi_fill_count += dnp->dn_blkptr[i].blk_fill;
+}
+
+void
+dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
+{
+	rw_enter(&dn->dn_struct_rwlock, RW_READER);
+	mutex_enter(&dn->dn_mtx);
+
+	__dmu_object_info_from_dnode(dn, doi);
 
 	mutex_exit(&dn->dn_mtx);
 	rw_exit(&dn->dn_struct_rwlock);
diff --git a/module/zfs/dmu_traverse.c b/module/zfs/dmu_traverse.c
index 32b3e50fc..1827ffc74 100644
--- a/module/zfs/dmu_traverse.c
+++ b/module/zfs/dmu_traverse.c
@@ -517,6 +517,9 @@ traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
 	mutex_init(&pd->pd_mtx, NULL, MUTEX_DEFAULT, NULL);
 	cv_init(&pd->pd_cv, NULL, CV_DEFAULT, NULL);
 
+	SET_BOOKMARK(czb, td->td_objset,
+	    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
+
 	/* See comment on ZIL traversal in dsl_scan_visitds. */
 	if (ds != NULL && !dsl_dataset_is_snapshot(ds) && !BP_IS_HOLE(rootbp)) {
 		uint32_t flags = ARC_WAIT;
@@ -525,7 +528,7 @@ traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
 
 		err = arc_read(NULL, td->td_spa, rootbp,
 		    arc_getbuf_func, &buf,
-		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, NULL);
+		    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, czb);
 		if (err != 0)
 			return (err);
 
@@ -539,8 +542,6 @@ traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
 	    td, TQ_NOQUEUE))
 		pd->pd_exited = B_TRUE;
 
-	SET_BOOKMARK(czb, td->td_objset,
-	    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
 	err = traverse_visitbp(td, NULL, rootbp, czb);
 
 	mutex_enter(&pd->pd_mtx);
diff --git a/module/zfs/dmu_tx.c b/module/zfs/dmu_tx.c
index 3e46a02f8..7b6223956 100644
--- a/module/zfs/dmu_tx.c
+++ b/module/zfs/dmu_tx.c
@@ -1077,7 +1077,7 @@ dmu_tx_unassign(dmu_tx_t *tx)
 int
 dmu_tx_assign(dmu_tx_t *tx, txg_how_t txg_how)
 {
-	hrtime_t before, after;
+	hrtime_t before;
 	int err;
 
 	ASSERT(tx->tx_txg == 0);
@@ -1100,10 +1100,7 @@ dmu_tx_assign(dmu_tx_t *tx, txg_how_t txg_how)
 
 	txg_rele_to_quiesce(&tx->tx_txgh);
 
-	after = gethrtime();
-
-	dsl_pool_tx_assign_add_usecs(tx->tx_pool,
-	    (after - before) / NSEC_PER_USEC);
+	spa_tx_assign_add_nsecs(tx->tx_pool->dp_spa, gethrtime() - before);
 
 	return (0);
 }
diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c
index da4a9df85..ffef9be75 100644
--- a/module/zfs/dsl_pool.c
+++ b/module/zfs/dsl_pool.c
@@ -48,7 +48,6 @@
 int zfs_no_write_throttle = 0;
 int zfs_write_limit_shift = 3;			/* 1/8th of physical memory */
 int zfs_txg_synctime_ms = 1000;		/* target millisecs to sync a txg */
-int zfs_txg_history = 60;		/* statistics for the last N txgs */
 
 unsigned long zfs_write_limit_min = 32 << 20;	/* min write limit is 32MB */
 unsigned long zfs_write_limit_max = 0;		/* max data payload per txg */
@@ -59,200 +58,6 @@ kmutex_t zfs_write_limit_lock;
 
 static pgcnt_t old_physmem = 0;
 
-static void
-dsl_pool_tx_assign_init(dsl_pool_t *dp, unsigned int ndata)
-{
-	kstat_named_t *ks;
-	char name[KSTAT_STRLEN];
-	int i, data_size = ndata * sizeof(kstat_named_t);
-
-	(void) snprintf(name, KSTAT_STRLEN, "dmu_tx_assign-%s",
-			spa_name(dp->dp_spa));
-
-	dp->dp_tx_assign_size = ndata;
-
-	if (data_size)
-		dp->dp_tx_assign_buckets = kmem_alloc(data_size, KM_SLEEP);
-	else
-		dp->dp_tx_assign_buckets = NULL;
-
-	for (i = 0; i < dp->dp_tx_assign_size; i++) {
-		ks = &dp->dp_tx_assign_buckets[i];
-		ks->data_type = KSTAT_DATA_UINT64;
-		ks->value.ui64 = 0;
-		(void) snprintf(ks->name, KSTAT_STRLEN, "%u us", 1 << i);
-	}
-
-	dp->dp_tx_assign_kstat = kstat_create("zfs", 0, name, "misc",
-	    KSTAT_TYPE_NAMED, 0, KSTAT_FLAG_VIRTUAL);
-
-	if (dp->dp_tx_assign_kstat) {
-		dp->dp_tx_assign_kstat->ks_data = dp->dp_tx_assign_buckets;
-		dp->dp_tx_assign_kstat->ks_ndata = dp->dp_tx_assign_size;
-		dp->dp_tx_assign_kstat->ks_data_size = data_size;
-		kstat_install(dp->dp_tx_assign_kstat);
-	}
-}
-
-static void
-dsl_pool_tx_assign_destroy(dsl_pool_t *dp)
-{
-	if (dp->dp_tx_assign_buckets)
-		kmem_free(dp->dp_tx_assign_buckets,
-			  dp->dp_tx_assign_size * sizeof(kstat_named_t));
-
-	if (dp->dp_tx_assign_kstat)
-		kstat_delete(dp->dp_tx_assign_kstat);
-}
-
-void
-dsl_pool_tx_assign_add_usecs(dsl_pool_t *dp, uint64_t usecs)
-{
-	uint64_t idx = 0;
-
-	while (((1 << idx) < usecs) && (idx < dp->dp_tx_assign_size - 1))
-		idx++;
-
-	atomic_inc_64(&dp->dp_tx_assign_buckets[idx].value.ui64);
-}
-
-static int
-dsl_pool_txg_history_update(kstat_t *ksp, int rw)
-{
-	dsl_pool_t *dp = ksp->ks_private;
-	txg_history_t *th;
-	int i = 0;
-
-	if (rw == KSTAT_WRITE)
-		return (EACCES);
-
-	if (ksp->ks_data)
-		kmem_free(ksp->ks_data, ksp->ks_data_size);
-
-	mutex_enter(&dp->dp_lock);
-
-	ksp->ks_ndata = dp->dp_txg_history_size;
-	ksp->ks_data_size = dp->dp_txg_history_size * sizeof(kstat_txg_t);
-	if (ksp->ks_data_size > 0)
-		ksp->ks_data = kmem_alloc(ksp->ks_data_size, KM_PUSHPAGE);
-
-	/* Traversed oldest to youngest for the most readable kstat output */
-	for (th = list_tail(&dp->dp_txg_history); th != NULL;
-	     th = list_prev(&dp->dp_txg_history, th)) {
-		mutex_enter(&th->th_lock);
-		ASSERT3S(i + sizeof(kstat_txg_t), <=, ksp->ks_data_size);
-		memcpy(ksp->ks_data + i, &th->th_kstat, sizeof(kstat_txg_t));
-		i += sizeof(kstat_txg_t);
-		mutex_exit(&th->th_lock);
-	}
-
-	mutex_exit(&dp->dp_lock);
-
-	return (0);
-}
-
-static void
-dsl_pool_txg_history_init(dsl_pool_t *dp, uint64_t txg)
-{
-	char name[KSTAT_STRLEN];
-
-	list_create(&dp->dp_txg_history, sizeof (txg_history_t),
-	    offsetof(txg_history_t, th_link));
-	dsl_pool_txg_history_add(dp, txg);
-
-	(void) snprintf(name, KSTAT_STRLEN, "txgs-%s", spa_name(dp->dp_spa));
-	dp->dp_txg_kstat = kstat_create("zfs", 0, name, "misc",
-	    KSTAT_TYPE_TXG, 0, KSTAT_FLAG_VIRTUAL);
-	if (dp->dp_txg_kstat) {
-		dp->dp_txg_kstat->ks_data = NULL;
-		dp->dp_txg_kstat->ks_private = dp;
-		dp->dp_txg_kstat->ks_update = dsl_pool_txg_history_update;
-		kstat_install(dp->dp_txg_kstat);
-	}
-}
-
-static void
-dsl_pool_txg_history_destroy(dsl_pool_t *dp)
-{
-	txg_history_t *th;
-
-	if (dp->dp_txg_kstat) {
-		if (dp->dp_txg_kstat->ks_data)
-			kmem_free(dp->dp_txg_kstat->ks_data,
-			    dp->dp_txg_kstat->ks_data_size);
-
-		kstat_delete(dp->dp_txg_kstat);
-	}
-
-	mutex_enter(&dp->dp_lock);
-	while ((th = list_remove_head(&dp->dp_txg_history))) {
-		dp->dp_txg_history_size--;
-		mutex_destroy(&th->th_lock);
-		kmem_free(th, sizeof(txg_history_t));
-	}
-
-	ASSERT3U(dp->dp_txg_history_size, ==, 0);
-	list_destroy(&dp->dp_txg_history);
-	mutex_exit(&dp->dp_lock);
-}
-
-txg_history_t *
-dsl_pool_txg_history_add(dsl_pool_t *dp, uint64_t txg)
-{
-	txg_history_t *th, *rm;
-
-	th = kmem_zalloc(sizeof(txg_history_t), KM_PUSHPAGE);
-	mutex_init(&th->th_lock, NULL, MUTEX_DEFAULT, NULL);
-	th->th_kstat.txg = txg;
-	th->th_kstat.state = TXG_STATE_OPEN;
-	th->th_kstat.birth = gethrtime();
-
-	mutex_enter(&dp->dp_lock);
-
-	list_insert_head(&dp->dp_txg_history, th);
-	dp->dp_txg_history_size++;
-
-	while (dp->dp_txg_history_size > zfs_txg_history) {
-		dp->dp_txg_history_size--;
-		rm = list_remove_tail(&dp->dp_txg_history);
-		mutex_destroy(&rm->th_lock);
-		kmem_free(rm, sizeof(txg_history_t));
-	}
-
-	mutex_exit(&dp->dp_lock);
-
-	return (th);
-}
-
-/*
- * Traversed youngest to oldest because lookups are only done for open
- * or syncing txgs which are guaranteed to be at the head of the list.
- * The txg_history_t structure will be returned locked.
- */
-txg_history_t *
-dsl_pool_txg_history_get(dsl_pool_t *dp, uint64_t txg)
-{
-	txg_history_t *th;
-
-	mutex_enter(&dp->dp_lock);
-	for (th = list_head(&dp->dp_txg_history); th != NULL;
-	     th = list_next(&dp->dp_txg_history, th)) {
-		if (th->th_kstat.txg == txg) {
-			mutex_enter(&th->th_lock);
-			break;
-		}
-	}
-	mutex_exit(&dp->dp_lock);
-
-	return (th);
-}
-
-void
-dsl_pool_txg_history_put(txg_history_t *th)
-{
-	mutex_exit(&th->th_lock);
-}
-
 int
 dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **ddp)
 {
@@ -295,9 +100,6 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg)
 	dp->dp_iput_taskq = taskq_create("zfs_iput_taskq", 1, minclsyspri,
 	    1, 4, 0);
 
-	dsl_pool_txg_history_init(dp, txg);
-	dsl_pool_tx_assign_init(dp, 32);
-
 	return (dp);
 }
 
@@ -438,8 +240,6 @@ dsl_pool_close(dsl_pool_t *dp)
 	arc_flush(dp->dp_spa);
 	txg_fini(dp);
 	dsl_scan_fini(dp);
-	dsl_pool_tx_assign_destroy(dp);
-	dsl_pool_txg_history_destroy(dp);
 	rrw_destroy(&dp->dp_config_rwlock);
 	mutex_destroy(&dp->dp_lock);
 	taskq_destroy(dp->dp_iput_taskq);
@@ -1241,9 +1041,6 @@ MODULE_PARM_DESC(zfs_write_limit_shift, "log2(fraction of memory) per txg");
 module_param(zfs_txg_synctime_ms, int, 0644);
 MODULE_PARM_DESC(zfs_txg_synctime_ms, "Target milliseconds between txg sync");
 
-module_param(zfs_txg_history, int, 0644);
-MODULE_PARM_DESC(zfs_txg_history, "Historic statistics for the last N txgs");
-
 module_param(zfs_write_limit_min, ulong, 0444);
 MODULE_PARM_DESC(zfs_write_limit_min, "Min txg write limit");
 
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index 9ba6e8963..a0b4797c9 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -48,6 +48,7 @@
 #include <sys/metaslab_impl.h>
 #include <sys/arc.h>
 #include <sys/ddt.h>
+#include <sys/kstat.h>
 #include "zfs_prop.h"
 #include "zfeature_common.h"
 
@@ -253,7 +254,6 @@ unsigned long zfs_deadman_synctime = 1000ULL;
  */
 int zfs_deadman_enabled = 1;
 
-
 /*
  * ==========================================================================
  * SPA config locking
@@ -495,6 +495,7 @@ spa_add(const char *name, nvlist_t *config, const char *altroot)
 
 	refcount_create(&spa->spa_refcount);
 	spa_config_lock_init(spa);
+	spa_stats_init(spa);
 
 	avl_add(&spa_namespace_avl, spa);
 
@@ -580,6 +581,7 @@ spa_remove(spa_t *spa)
 
 	refcount_destroy(&spa->spa_refcount);
 
+	spa_stats_destroy(spa);
 	spa_config_lock_destroy(spa);
 
 	for (t = 0; t < TXG_SIZE; t++)
diff --git a/module/zfs/spa_stats.c b/module/zfs/spa_stats.c
new file mode 100644
index 000000000..789e8c3e6
--- /dev/null
+++ b/module/zfs/spa_stats.c
@@ -0,0 +1,636 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/spa_impl.h>
+
+/*
+ * Keeps stats on last N reads per spa_t, disabled by default.
+ */
+int zfs_read_history = 0;
+
+/*
+ * Include cache hits in history, disabled by default.
+ */
+int zfs_read_history_hits = 0;
+
+/*
+ * Keeps stats on the last N txgs, disabled by default.
+ */
+int zfs_txg_history = 0;
+
+/*
+ * ==========================================================================
+ * SPA Read History Routines
+ * ==========================================================================
+ */
+
+/*
+ * Read statistics - Information exported regarding each arc_read call
+ */
+typedef struct spa_read_history {
+	uint64_t	uid;		/* unique identifier */
+	hrtime_t	start;		/* time read completed */
+	uint64_t	objset;		/* read from this objset */
+	uint64_t	object;		/* read of this object number */
+	uint64_t	level;		/* block's indirection level */
+	uint64_t	blkid;		/* read of this block id */
+	char		origin[24];	/* read originated from here */
+	uint32_t	aflags;		/* ARC flags (cached, prefetch, etc.) */
+	pid_t		pid;		/* PID of task doing read */
+	char		comm[16];	/* process name of task doing read */
+	list_node_t	srh_link;
+} spa_read_history_t;
+
+static int
+spa_read_history_headers(char *buf, size_t size)
+{
+	size = snprintf(buf, size - 1, "%-8s %-16s %-8s %-8s %-8s %-8s %-8s "
+	    "%-24s %-8s %-16s\n", "UID", "start", "objset", "object",
+	    "level", "blkid", "aflags", "origin", "pid", "process");
+	buf[size] = '\0';
+
+	return (0);
+}
+
+static int
+spa_read_history_data(char *buf, size_t size, void *data)
+{
+	spa_read_history_t *srh = (spa_read_history_t *)data;
+
+	size = snprintf(buf, size - 1, "%-8llu %-16llu 0x%-6llx "
+	    "%-8lli %-8lli %-8lli 0x%-6x %-24s %-8i %-16s\n",
+	    (u_longlong_t)srh->uid, srh->start,
+	    (longlong_t)srh->objset, (longlong_t)srh->object,
+	    (longlong_t)srh->level, (longlong_t)srh->blkid,
+	    srh->aflags, srh->origin, srh->pid, srh->comm);
+	buf[size] = '\0';
+
+	return (0);
+}
+
+/*
+ * Calculate the address for the next spa_stats_history_t entry.  The
+ * ssh->lock will be held until ksp->ks_ndata entries are processed.
+ */
+static void *
+spa_read_history_addr(kstat_t *ksp, loff_t n)
+{
+	spa_t *spa = ksp->ks_private;
+	spa_stats_history_t *ssh = &spa->spa_stats.read_history;
+
+	ASSERT(MUTEX_HELD(&ssh->lock));
+
+	if (n == 0)
+		ssh->private = list_tail(&ssh->list);
+	else if (ssh->private)
+		ssh->private = list_prev(&ssh->list, ssh->private);
+
+	return (ssh->private);
+}
+
+/*
+ * When the kstat is written discard all spa_read_history_t entires.  The
+ * ssh->lock will be held until ksp->ks_ndata entries are processed.
+ */
+static int
+spa_read_history_update(kstat_t *ksp, int rw)
+{
+	spa_t *spa = ksp->ks_private;
+	spa_stats_history_t *ssh = &spa->spa_stats.read_history;
+
+	if (rw == KSTAT_WRITE) {
+		spa_read_history_t *srh;
+
+		while ((srh = list_remove_head(&ssh->list))) {
+			ssh->size--;
+			kmem_free(srh, sizeof(spa_read_history_t));
+		}
+
+		ASSERT3U(ssh->size, ==, 0);
+	}
+
+	ksp->ks_ndata = ssh->size;
+	ksp->ks_data_size = ssh->size * sizeof(spa_read_history_t);
+
+	return (0);
+}
+
+static void
+spa_read_history_init(spa_t *spa)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.read_history;
+	char name[KSTAT_STRLEN];
+	kstat_t *ksp;
+
+	mutex_init(&ssh->lock, NULL, MUTEX_DEFAULT, NULL);
+	list_create(&ssh->list, sizeof (spa_read_history_t),
+	    offsetof(spa_read_history_t, srh_link));
+
+	ssh->count = 0;
+	ssh->size = 0;
+	ssh->private = NULL;
+
+	(void) snprintf(name, KSTAT_STRLEN, "zfs/%s", spa_name(spa));
+	name[KSTAT_STRLEN-1] = '\0';
+
+	ksp = kstat_create(name, 0, "reads", "misc",
+	    KSTAT_TYPE_RAW, 0, KSTAT_FLAG_VIRTUAL);
+	ssh->kstat = ksp;
+
+	if (ksp) {
+		ksp->ks_lock = &ssh->lock;
+		ksp->ks_data = NULL;
+		ksp->ks_private = spa;
+		ksp->ks_update = spa_read_history_update;
+		kstat_set_raw_ops(ksp, spa_read_history_headers,
+		    spa_read_history_data, spa_read_history_addr);
+		kstat_install(ksp);
+	}
+}
+
+static void
+spa_read_history_destroy(spa_t *spa)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.read_history;
+	spa_read_history_t *srh;
+	kstat_t *ksp;
+
+	ksp = ssh->kstat;
+	if (ksp)
+		kstat_delete(ksp);
+
+	mutex_enter(&ssh->lock);
+	while ((srh = list_remove_head(&ssh->list))) {
+		ssh->size--;
+		kmem_free(srh, sizeof(spa_read_history_t));
+	}
+
+	ASSERT3U(ssh->size, ==, 0);
+	list_destroy(&ssh->list);
+	mutex_exit(&ssh->lock);
+
+	mutex_destroy(&ssh->lock);
+}
+
+void
+spa_read_history_add(spa_t *spa, const zbookmark_t *zb, uint32_t aflags)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.read_history;
+	spa_read_history_t *srh, *rm;
+
+	ASSERT3P(spa, !=, NULL);
+	ASSERT3P(zb,  !=, NULL);
+
+	if (zfs_read_history == 0 && ssh->size == 0)
+		return;
+
+	if (zfs_read_history_hits == 0 && (aflags & ARC_CACHED))
+		return;
+
+	srh = kmem_zalloc(sizeof(spa_read_history_t), KM_PUSHPAGE);
+	strlcpy(srh->origin, zb->zb_func, sizeof(srh->origin));
+	strlcpy(srh->comm, getcomm(), sizeof(srh->comm));
+	srh->start  = gethrtime();
+	srh->objset = zb->zb_objset;
+	srh->object = zb->zb_object;
+	srh->level  = zb->zb_level;
+	srh->blkid  = zb->zb_blkid;
+	srh->aflags = aflags;
+	srh->pid    = getpid();
+
+	mutex_enter(&ssh->lock);
+
+	srh->uid = ssh->count++;
+	list_insert_head(&ssh->list, srh);
+	ssh->size++;
+
+	while (ssh->size > zfs_read_history) {
+		ssh->size--;
+		rm = list_remove_tail(&ssh->list);
+		kmem_free(rm, sizeof(spa_read_history_t));
+	}
+
+	mutex_exit(&ssh->lock);
+}
+
+/*
+ * ==========================================================================
+ * SPA TXG History Routines
+ * ==========================================================================
+ */
+
+/*
+ * Txg statistics - Information exported regarding each txg sync
+ */
+
+typedef struct spa_txg_history {
+	uint64_t	txg;		/* txg id */
+	txg_state_t	state;		/* active txg state */
+	uint64_t	nread;		/* number of bytes read */
+	uint64_t	nwritten;	/* number of bytes written */
+	uint64_t	reads;		/* number of read operations */
+	uint64_t	writes;		/* number of write operations */
+	uint64_t	nreserved;	/* number of bytes reserved */
+	hrtime_t	times[TXG_STATE_COMMITTED]; /* completion times */
+	list_node_t	sth_link;
+} spa_txg_history_t;
+
+static int
+spa_txg_history_headers(char *buf, size_t size)
+{
+	size = snprintf(buf, size - 1, "%-8s %-16s %-5s %-12s %-12s %-12s "
+	    "%-8s %-8s %-12s %-12s %-12s\n", "txg", "birth", "state",
+	    "nreserved", "nread", "nwritten", "reads", "writes",
+	    "otime", "qtime", "stime");
+	buf[size] = '\0';
+
+	return (0);
+}
+
+static int
+spa_txg_history_data(char *buf, size_t size, void *data)
+{
+	spa_txg_history_t *sth = (spa_txg_history_t *)data;
+	uint64_t open = 0, quiesce = 0, sync = 0;
+	char state;
+
+	switch (sth->state) {
+		case TXG_STATE_BIRTH:		state = 'B';	break;
+		case TXG_STATE_OPEN:		state = 'O';	break;
+		case TXG_STATE_QUIESCED:	state = 'Q';	break;
+		case TXG_STATE_SYNCED:		state = 'S';	break;
+		case TXG_STATE_COMMITTED:	state = 'C';	break;
+		default:			state = '?';	break;
+	}
+
+	if (sth->times[TXG_STATE_OPEN])
+		open = sth->times[TXG_STATE_OPEN] -
+		    sth->times[TXG_STATE_BIRTH];
+
+	if (sth->times[TXG_STATE_QUIESCED])
+		quiesce = sth->times[TXG_STATE_QUIESCED] -
+		    sth->times[TXG_STATE_OPEN];
+
+	if (sth->times[TXG_STATE_SYNCED])
+		sync = sth->times[TXG_STATE_SYNCED] -
+		    sth->times[TXG_STATE_QUIESCED];
+
+	size = snprintf(buf, size - 1, "%-8llu %-16llu %-5c %-12llu "
+	    "%-12llu %-12llu %-8llu %-8llu %-12llu %-12llu %-12llu\n",
+	    (longlong_t)sth->txg, sth->times[TXG_STATE_BIRTH], state,
+	    (u_longlong_t)sth->nreserved,
+	    (u_longlong_t)sth->nread, (u_longlong_t)sth->nwritten,
+	    (u_longlong_t)sth->reads, (u_longlong_t)sth->writes,
+	    (u_longlong_t)open, (u_longlong_t)quiesce, (u_longlong_t)sync);
+	buf[size] = '\0';
+
+	return (0);
+}
+
+/*
+ * Calculate the address for the next spa_stats_history_t entry.  The
+ * ssh->lock will be held until ksp->ks_ndata entries are processed.
+ */
+static void *
+spa_txg_history_addr(kstat_t *ksp, loff_t n)
+{
+	spa_t *spa = ksp->ks_private;
+	spa_stats_history_t *ssh = &spa->spa_stats.txg_history;
+
+	ASSERT(MUTEX_HELD(&ssh->lock));
+
+	if (n == 0)
+		ssh->private = list_tail(&ssh->list);
+	else if (ssh->private)
+		ssh->private = list_prev(&ssh->list, ssh->private);
+
+	return (ssh->private);
+}
+
+/*
+ * When the kstat is written discard all spa_txg_history_t entires.  The
+ * ssh->lock will be held until ksp->ks_ndata entries are processed.
+ */
+static int
+spa_txg_history_update(kstat_t *ksp, int rw)
+{
+	spa_t *spa = ksp->ks_private;
+	spa_stats_history_t *ssh = &spa->spa_stats.txg_history;
+
+	ASSERT(MUTEX_HELD(&ssh->lock));
+
+	if (rw == KSTAT_WRITE) {
+		spa_txg_history_t *sth;
+
+		while ((sth = list_remove_head(&ssh->list))) {
+			ssh->size--;
+			kmem_free(sth, sizeof(spa_txg_history_t));
+		}
+
+		ASSERT3U(ssh->size, ==, 0);
+	}
+
+	ksp->ks_ndata = ssh->size;
+	ksp->ks_data_size = ssh->size * sizeof(spa_txg_history_t);
+
+	return (0);
+}
+
+static void
+spa_txg_history_init(spa_t *spa)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.txg_history;
+	char name[KSTAT_STRLEN];
+	kstat_t *ksp;
+
+	mutex_init(&ssh->lock, NULL, MUTEX_DEFAULT, NULL);
+	list_create(&ssh->list, sizeof (spa_txg_history_t),
+	    offsetof(spa_txg_history_t, sth_link));
+
+	ssh->count = 0;
+	ssh->size = 0;
+	ssh->private = NULL;
+
+	(void) snprintf(name, KSTAT_STRLEN, "zfs/%s", spa_name(spa));
+	name[KSTAT_STRLEN-1] = '\0';
+
+	ksp = kstat_create(name, 0, "txgs", "misc",
+	    KSTAT_TYPE_RAW, 0, KSTAT_FLAG_VIRTUAL);
+	ssh->kstat = ksp;
+
+	if (ksp) {
+		ksp->ks_lock = &ssh->lock;
+		ksp->ks_data = NULL;
+		ksp->ks_private = spa;
+		ksp->ks_update = spa_txg_history_update;
+		kstat_set_raw_ops(ksp, spa_txg_history_headers,
+		    spa_txg_history_data, spa_txg_history_addr);
+		kstat_install(ksp);
+	}
+}
+
+static void
+spa_txg_history_destroy(spa_t *spa)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.txg_history;
+	spa_txg_history_t *sth;
+	kstat_t *ksp;
+
+	ksp = ssh->kstat;
+	if (ksp)
+		kstat_delete(ksp);
+
+	mutex_enter(&ssh->lock);
+	while ((sth = list_remove_head(&ssh->list))) {
+		ssh->size--;
+		kmem_free(sth, sizeof(spa_txg_history_t));
+	}
+
+	ASSERT3U(ssh->size, ==, 0);
+	list_destroy(&ssh->list);
+	mutex_exit(&ssh->lock);
+
+	mutex_destroy(&ssh->lock);
+}
+
+/*
+ * Add a new txg to historical record.
+ */
+void
+spa_txg_history_add(spa_t *spa, uint64_t txg)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.txg_history;
+	spa_txg_history_t *sth, *rm;
+
+	if (zfs_txg_history == 0 && ssh->size == 0)
+		return;
+
+	sth = kmem_zalloc(sizeof(spa_txg_history_t), KM_PUSHPAGE);
+	sth->txg = txg;
+	sth->state = TXG_STATE_OPEN;
+	sth->times[TXG_STATE_BIRTH] = gethrtime();
+
+	mutex_enter(&ssh->lock);
+
+	list_insert_head(&ssh->list, sth);
+	ssh->size++;
+
+	while (ssh->size > zfs_txg_history) {
+		ssh->size--;
+		rm = list_remove_tail(&ssh->list);
+		kmem_free(rm, sizeof(spa_txg_history_t));
+	}
+
+	mutex_exit(&ssh->lock);
+}
+
+/*
+ * Set txg state completion time and increment current state.
+ */
+int
+spa_txg_history_set(spa_t *spa, uint64_t txg, txg_state_t completed_state,
+    hrtime_t completed_time)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.txg_history;
+	spa_txg_history_t *sth;
+	int error = ENOENT;
+
+	if (zfs_txg_history == 0)
+		return (0);
+
+	mutex_enter(&ssh->lock);
+	for (sth = list_head(&ssh->list); sth != NULL;
+	     sth = list_next(&ssh->list, sth)) {
+		if (sth->txg == txg) {
+			sth->times[completed_state] = completed_time;
+			sth->state++;
+			error = 0;
+			break;
+		}
+	}
+	mutex_exit(&ssh->lock);
+
+	return (error);
+}
+
+/*
+ * Set txg IO stats.
+ */
+int
+spa_txg_history_set_io(spa_t *spa, uint64_t txg, uint64_t nread,
+    uint64_t nwritten, uint64_t reads, uint64_t writes, uint64_t nreserved)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.txg_history;
+	spa_txg_history_t *sth;
+	int error = ENOENT;
+
+	if (zfs_txg_history == 0)
+		return (0);
+
+	mutex_enter(&ssh->lock);
+	for (sth = list_head(&ssh->list); sth != NULL;
+	     sth = list_next(&ssh->list, sth)) {
+		if (sth->txg == txg) {
+			sth->nread = nread;
+			sth->nwritten = nwritten;
+			sth->reads = reads;
+			sth->writes = writes;
+			sth->nreserved = nreserved;
+			error = 0;
+			break;
+		}
+	}
+	mutex_exit(&ssh->lock);
+
+	return (error);
+}
+
+/*
+ * ==========================================================================
+ * SPA TX Assign Histogram Routines
+ * ==========================================================================
+ */
+
+/*
+ * Tx statistics - Information exported regarding dmu_tx_assign time.
+ */
+
+/*
+ * When the kstat is written zero all buckets.  When the kstat is read
+ * count the number of trailing buckets set to zero and update ks_ndata
+ * such that they are not output.
+ */
+static int
+spa_tx_assign_update(kstat_t *ksp, int rw)
+{
+	spa_t *spa = ksp->ks_private;
+	spa_stats_history_t *ssh = &spa->spa_stats.tx_assign_histogram;
+	int i;
+
+	if (rw == KSTAT_WRITE) {
+		for (i = 0; i < ssh->count; i++)
+			((kstat_named_t *)ssh->private)[i].value.ui64 = 0;
+	}
+
+	for (i = ssh->count; i > 0; i--)
+		if (((kstat_named_t *)ssh->private)[i-1].value.ui64 != 0)
+			break;
+
+	ksp->ks_ndata = i;
+	ksp->ks_data_size = i * sizeof(kstat_named_t);
+
+	return (0);
+}
+
+static void
+spa_tx_assign_init(spa_t *spa)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.tx_assign_histogram;
+	char name[KSTAT_STRLEN];
+	kstat_named_t *ks;
+	kstat_t *ksp;
+	int i;
+
+	mutex_init(&ssh->lock, NULL, MUTEX_DEFAULT, NULL);
+
+	ssh->count = 42; /* power of two buckets for 1ns to 2,199s */
+	ssh->size = ssh->count * sizeof(kstat_named_t);
+	ssh->private = kmem_alloc(ssh->size, KM_SLEEP);
+
+	(void) snprintf(name, KSTAT_STRLEN, "zfs/%s", spa_name(spa));
+	name[KSTAT_STRLEN-1] = '\0';
+
+	for (i = 0; i < ssh->count; i++) {
+		ks = &((kstat_named_t *)ssh->private)[i];
+		ks->data_type = KSTAT_DATA_UINT64;
+		ks->value.ui64 = 0;
+		(void) snprintf(ks->name, KSTAT_STRLEN, "%llu ns",
+		    (u_longlong_t)1 << i);
+	}
+
+	ksp = kstat_create(name, 0, "dmu_tx_assign", "misc",
+	    KSTAT_TYPE_NAMED, 0, KSTAT_FLAG_VIRTUAL);
+	ssh->kstat = ksp;
+
+	if (ksp) {
+		ksp->ks_lock = &ssh->lock;
+		ksp->ks_data = ssh->private;
+		ksp->ks_ndata = ssh->count;
+		ksp->ks_data_size = ssh->size;
+		ksp->ks_private = spa;
+		ksp->ks_update = spa_tx_assign_update;
+		kstat_install(ksp);
+	}
+}
+
+static void
+spa_tx_assign_destroy(spa_t *spa)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.tx_assign_histogram;
+	kstat_t *ksp;
+
+	ksp = ssh->kstat;
+	if (ksp)
+		kstat_delete(ksp);
+
+	kmem_free(ssh->private, ssh->size);
+	mutex_destroy(&ssh->lock);
+}
+
+void
+spa_tx_assign_add_nsecs(spa_t *spa, uint64_t nsecs)
+{
+	spa_stats_history_t *ssh = &spa->spa_stats.tx_assign_histogram;
+	uint64_t idx = 0;
+
+	while (((1 << idx) < nsecs) && (idx < ssh->size - 1))
+		idx++;
+
+	atomic_inc_64(&((kstat_named_t *)ssh->private)[idx].value.ui64);
+}
+
+void
+spa_stats_init(spa_t *spa)
+{
+	spa_read_history_init(spa);
+	spa_txg_history_init(spa);
+	spa_tx_assign_init(spa);
+}
+
+void
+spa_stats_destroy(spa_t *spa)
+{
+	spa_tx_assign_destroy(spa);
+	spa_txg_history_destroy(spa);
+	spa_read_history_destroy(spa);
+}
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+module_param(zfs_read_history, int, 0644);
+MODULE_PARM_DESC(zfs_read_history, "Historic statistics for the last N reads");
+
+module_param(zfs_read_history_hits, int, 0644);
+MODULE_PARM_DESC(zfs_read_history_hits, "Include cache hits in read history");
+
+module_param(zfs_txg_history, int, 0644);
+MODULE_PARM_DESC(zfs_txg_history, "Historic statistics for the last N txgs");
+#endif
diff --git a/module/zfs/txg.c b/module/zfs/txg.c
index b3e537f45..7a3da8647 100644
--- a/module/zfs/txg.c
+++ b/module/zfs/txg.c
@@ -27,11 +27,11 @@
 #include <sys/zfs_context.h>
 #include <sys/txg_impl.h>
 #include <sys/dmu_impl.h>
+#include <sys/spa_impl.h>
 #include <sys/dmu_tx.h>
 #include <sys/dsl_pool.h>
 #include <sys/dsl_scan.h>
 #include <sys/callb.h>
-#include <sys/spa_impl.h>
 
 /*
  * ZFS Transaction Groups
@@ -351,8 +351,6 @@ txg_rele_to_sync(txg_handle_t *th)
 static void
 txg_quiesce(dsl_pool_t *dp, uint64_t txg)
 {
-	hrtime_t start;
-	txg_history_t *th;
 	tx_state_t *tx = &dp->dp_tx;
 	int g = txg & TXG_MASK;
 	int c;
@@ -366,6 +364,9 @@ txg_quiesce(dsl_pool_t *dp, uint64_t txg)
 	ASSERT(txg == tx->tx_open_txg);
 	tx->tx_open_txg++;
 
+	spa_txg_history_set(dp->dp_spa, txg, TXG_STATE_OPEN, gethrtime());
+	spa_txg_history_add(dp->dp_spa, tx->tx_open_txg);
+
 	/*
 	 * Now that we've incremented tx_open_txg, we can let threads
 	 * enter the next transaction group.
@@ -374,19 +375,8 @@ txg_quiesce(dsl_pool_t *dp, uint64_t txg)
 		mutex_exit(&tx->tx_cpu[c].tc_lock);
 
 	/*
-	 * Measure how long the txg was open and replace the kstat.
-	 */
-	th = dsl_pool_txg_history_get(dp, txg);
-	th->th_kstat.open_time = gethrtime() - th->th_kstat.birth;
-	th->th_kstat.state = TXG_STATE_QUIESCING;
-	dsl_pool_txg_history_put(th);
-	dsl_pool_txg_history_add(dp, tx->tx_open_txg);
-
-	/*
 	 * Quiesce the transaction group by waiting for everyone to txg_exit().
 	 */
-	start = gethrtime();
-
 	for (c = 0; c < max_ncpus; c++) {
 		tx_cpu_t *tc = &tx->tx_cpu[c];
 		mutex_enter(&tc->tc_lock);
@@ -395,12 +385,7 @@ txg_quiesce(dsl_pool_t *dp, uint64_t txg)
 		mutex_exit(&tc->tc_lock);
 	}
 
-	/*
-	 * Measure how long the txg took to quiesce.
-	 */
-	th = dsl_pool_txg_history_get(dp, txg);
-	th->th_kstat.quiesce_time = gethrtime() - start;
-	dsl_pool_txg_history_put(th);
+	spa_txg_history_set(dp->dp_spa, txg, TXG_STATE_QUIESCED, gethrtime());
 }
 
 static void
@@ -472,6 +457,7 @@ txg_sync_thread(dsl_pool_t *dp)
 	spa_t *spa = dp->dp_spa;
 	tx_state_t *tx = &dp->dp_tx;
 	callb_cpr_t cpr;
+	vdev_stat_t *vs1, *vs2;
 	uint64_t start, delta;
 
 #ifdef _KERNEL
@@ -485,10 +471,11 @@ txg_sync_thread(dsl_pool_t *dp)
 
 	txg_thread_enter(tx, &cpr);
 
+	vs1 = kmem_alloc(sizeof(vdev_stat_t), KM_PUSHPAGE);
+	vs2 = kmem_alloc(sizeof(vdev_stat_t), KM_PUSHPAGE);
+
 	start = delta = 0;
 	for (;;) {
-		hrtime_t hrstart;
-		txg_history_t *th;
 		uint64_t timer, timeout;
 		uint64_t txg;
 
@@ -522,8 +509,13 @@ txg_sync_thread(dsl_pool_t *dp)
 			txg_thread_wait(tx, &cpr, &tx->tx_quiesce_done_cv, 0);
 		}
 
-		if (tx->tx_exiting)
+		if (tx->tx_exiting) {
+			kmem_free(vs2, sizeof(vdev_stat_t));
+			kmem_free(vs1, sizeof(vdev_stat_t));
 			txg_thread_exit(tx, &cpr, &tx->tx_sync_thread);
+		}
+
+		vdev_get_stats(spa->spa_root_vdev, vs1);
 
 		/*
 		 * Consume the quiesced txg which has been handed off to
@@ -535,17 +527,11 @@ txg_sync_thread(dsl_pool_t *dp)
 		tx->tx_syncing_txg = txg;
 		cv_broadcast(&tx->tx_quiesce_more_cv);
 
-		th = dsl_pool_txg_history_get(dp, txg);
-		th->th_kstat.state = TXG_STATE_SYNCING;
-		vdev_get_stats(spa->spa_root_vdev, &th->th_vs1);
-		dsl_pool_txg_history_put(th);
-
 		dprintf("txg=%llu quiesce_txg=%llu sync_txg=%llu\n",
 		    txg, tx->tx_quiesce_txg_waiting, tx->tx_sync_txg_waiting);
 		mutex_exit(&tx->tx_sync_lock);
 
 		start = ddi_get_lbolt();
-		hrstart = gethrtime();
 		spa_sync(spa, txg);
 		delta = ddi_get_lbolt() - start;
 
@@ -559,22 +545,15 @@ txg_sync_thread(dsl_pool_t *dp)
 		 */
 		txg_dispatch_callbacks(dp, txg);
 
-		/*
-		 * Measure the txg sync time determine the amount of I/O done.
-		 */
-		th = dsl_pool_txg_history_get(dp, txg);
-		vdev_get_stats(spa->spa_root_vdev, &th->th_vs2);
-		th->th_kstat.sync_time = gethrtime() - hrstart;
-		th->th_kstat.nread = th->th_vs2.vs_bytes[ZIO_TYPE_READ] -
-		    th->th_vs1.vs_bytes[ZIO_TYPE_READ];
-		th->th_kstat.nwritten = th->th_vs2.vs_bytes[ZIO_TYPE_WRITE] -
-		    th->th_vs1.vs_bytes[ZIO_TYPE_WRITE];
-		th->th_kstat.reads = th->th_vs2.vs_ops[ZIO_TYPE_READ] -
-		    th->th_vs1.vs_ops[ZIO_TYPE_READ];
-		th->th_kstat.writes = th->th_vs2.vs_ops[ZIO_TYPE_WRITE] -
-		    th->th_vs1.vs_ops[ZIO_TYPE_WRITE];
-		th->th_kstat.state = TXG_STATE_COMMITTED;
-		dsl_pool_txg_history_put(th);
+		vdev_get_stats(spa->spa_root_vdev, vs2);
+		spa_txg_history_set_io(spa, txg,
+		    vs2->vs_bytes[ZIO_TYPE_READ]-vs1->vs_bytes[ZIO_TYPE_READ],
+		    vs2->vs_bytes[ZIO_TYPE_WRITE]-vs1->vs_bytes[ZIO_TYPE_WRITE],
+		    vs2->vs_ops[ZIO_TYPE_READ]-vs1->vs_ops[ZIO_TYPE_READ],
+		    vs2->vs_ops[ZIO_TYPE_WRITE]-vs1->vs_ops[ZIO_TYPE_WRITE],
+		    dp->dp_space_towrite[txg & TXG_MASK] +
+		    dp->dp_tempreserved[txg & TXG_MASK] / 2);
+		spa_txg_history_set(spa, txg, TXG_STATE_SYNCED, gethrtime());
 	}
 }