path: root/cmd/arc_summary/arc_summary.py

#!/usr/bin/python
#
# $Id: arc_summary.pl,v 388:e27800740aa2 2011-07-08 02:53:29Z jhell $
#
# Copyright (c) 2008 Ben Rockwood <benr@cuddletech.com>,
# Copyright (c) 2010 Martin Matuska <mm@FreeBSD.org>,
# Copyright (c) 2010-2011 Jason J. Hellenthal <jhell@DataIX.net>,
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# If you are having troubles when using this script from cron(8) please try
# adjusting your PATH before reporting problems.
#
# /usr/bin & /sbin
#
# Binaries used are:
#
# dc(1), kldstat(8), sed(1), sysctl(8) & vmstat(8)
#
# Binaries that I am working on phasing out are:
#
# dc(1) & sed(1)

import sys
import time
import getopt
import re
from os import listdir
from subprocess import Popen, PIPE
from decimal import Decimal as D


usetunable = True
show_tunable_descriptions = False
alternate_tunable_layout = False
kstat_pobj = re.compile("^([^:]+):\s+(.+)\s*$", flags=re.M)


def get_Kstat():
    def load_proc_kstats(fn, namespace):
        kstats = [line.strip() for line in open(fn)]
        del kstats[0:2]
        for kstat in kstats:
            kstat = kstat.strip()
            name, unused, value = kstat.split()
            Kstat[namespace + name] = D(value)

    Kstat = {}
    load_proc_kstats('/proc/spl/kstat/zfs/arcstats',
                     'kstat.zfs.misc.arcstats.')
    load_proc_kstats('/proc/spl/kstat/zfs/zfetchstats',
                     'kstat.zfs.misc.zfetchstats.')
    load_proc_kstats('/proc/spl/kstat/zfs/vdev_cache_stats',
                     'kstat.zfs.misc.vdev_cache_stats.')

    return Kstat


def div1():
    sys.stdout.write("\n")
    for i in range(18):
        sys.stdout.write("%s" % "----")
    sys.stdout.write("\n")


def div2():
    sys.stdout.write("\n")


def fBytes(b=0):
    """Return human-readable representation of a byte value in
    powers of 2 (eg "KiB" for "kibibytes", etc) to two decimal
    points. Values smaller than one KiB are returned without
    decimal points.
    """

    prefixes = [
        [2**80, "YiB"],   # yobibytes (yotta)
        [2**70, "ZiB"],   # zebibytes (zetta)
        [2**60, "EiB"],   # exbibytes (exa)
        [2**50, "PiB"],   # pebibytes (peta)
        [2**40, "TiB"],   # tebibytes (tera)
        [2**30, "GiB"],   # gibibytes (giga)
        [2**20, "MiB"],   # mebibytes (mega)
        [2**10, "KiB"]]   # kibibytes (kilo)

    if b >= 2**10:

        for limit, unit in prefixes:

            if b >= limit:
                value = b / limit
                break

        result = "%0.2f\t%s" % (value, unit)

    else:

        result = "%d\tBytes" % b

    return result


def fHits(Hits=0, Decimal=2):
    khits = (10 ** 3)
    mhits = (10 ** 6)
    bhits = (10 ** 9)
    thits = (10 ** 12)
    qhits = (10 ** 15)
    Qhits = (10 ** 18)
    shits = (10 ** 21)
    Shits = (10 ** 24)

    if Hits >= Shits:
        return str("%0." + str(Decimal) + "f") % (Hits / Shits) + "S"
    elif Hits >= shits:
        return str("%0." + str(Decimal) + "f") % (Hits / shits) + "s"
    elif Hits >= Qhits:
        return str("%0." + str(Decimal) + "f") % (Hits / Qhits) + "Q"
    elif Hits >= qhits:
        return str("%0." + str(Decimal) + "f") % (Hits / qhits) + "q"
    elif Hits >= thits:
        return str("%0." + str(Decimal) + "f") % (Hits / thits) + "t"
    elif Hits >= bhits:
        return str("%0." + str(Decimal) + "f") % (Hits / bhits) + "b"
    elif Hits >= mhits:
        return str("%0." + str(Decimal) + "f") % (Hits / mhits) + "m"
    elif Hits >= khits:
        return str("%0." + str(Decimal) + "f") % (Hits / khits) + "k"
    elif Hits == 0:
        return str("%d" % 0)
    else:
        return str("%d" % Hits)


def fPerc(lVal=0, rVal=0, Decimal=2):
    if rVal > 0:
        return str("%0." + str(Decimal) + "f") % (100 * (lVal / rVal)) + "%"
    else:
        return str("%0." + str(Decimal) + "f") % 100 + "%"


def get_arc_summary(Kstat):

    output = {}
    memory_throttle_count = Kstat[
        "kstat.zfs.misc.arcstats.memory_throttle_count"
        ]

    if memory_throttle_count > 0:
        output['health'] = 'THROTTLED'
    else:
        output['health'] = 'HEALTHY'

    output['memory_throttle_count'] = fHits(memory_throttle_count)

    # ARC Misc.
    deleted = Kstat["kstat.zfs.misc.arcstats.deleted"]
    mutex_miss = Kstat["kstat.zfs.misc.arcstats.mutex_miss"]

    # ARC Misc.
    output["arc_misc"] = {}
    output["arc_misc"]["deleted"] = fHits(deleted)
    output["arc_misc"]['mutex_miss'] = fHits(mutex_miss)
    output["arc_misc"]['evict_skips'] = fHits(mutex_miss)

    # ARC Sizing
    arc_size = Kstat["kstat.zfs.misc.arcstats.size"]
    mru_size = Kstat["kstat.zfs.misc.arcstats.mru_size"]
    mfu_size = Kstat["kstat.zfs.misc.arcstats.mfu_size"]
    target_max_size = Kstat["kstat.zfs.misc.arcstats.c_max"]
    target_min_size = Kstat["kstat.zfs.misc.arcstats.c_min"]
    target_size = Kstat["kstat.zfs.misc.arcstats.c"]

    target_size_ratio = (target_max_size / target_min_size)

    # ARC Sizing
    output['arc_sizing'] = {}
    output['arc_sizing']['arc_size'] = {
        'per': fPerc(arc_size, target_max_size),
        'num': fBytes(arc_size),
    }
    output['arc_sizing']['target_max_size'] = {
        'ratio': target_size_ratio,
        'num': fBytes(target_max_size),
    }
    output['arc_sizing']['target_min_size'] = {
        'per': fPerc(target_min_size, target_max_size),
        'num': fBytes(target_min_size),
    }
    output['arc_sizing']['target_size'] = {
        'per': fPerc(target_size, target_max_size),
        'num': fBytes(target_size),
    }

    # ARC Hash Breakdown
    output['arc_hash_break'] = {}
    output['arc_hash_break']['hash_chain_max'] = Kstat[
        "kstat.zfs.misc.arcstats.hash_chain_max"
        ]
    output['arc_hash_break']['hash_chains'] = Kstat[
        "kstat.zfs.misc.arcstats.hash_chains"
        ]
    output['arc_hash_break']['hash_collisions'] = Kstat[
        "kstat.zfs.misc.arcstats.hash_collisions"
        ]
    output['arc_hash_break']['hash_elements'] = Kstat[
        "kstat.zfs.misc.arcstats.hash_elements"
        ]
    output['arc_hash_break']['hash_elements_max'] = Kstat[
        "kstat.zfs.misc.arcstats.hash_elements_max"
        ]

    output['arc_size_break'] = {}
    output['arc_size_break']['recently_used_cache_size'] = {
        'per': fPerc(mru_size, mru_size + mfu_size),
        'num': fBytes(mru_size),
    }
    output['arc_size_break']['frequently_used_cache_size'] = {
        'per': fPerc(mfu_size, mru_size + mfu_size),
        'num': fBytes(mfu_size),
    }

    # ARC Hash Breakdown
    hash_chain_max = Kstat["kstat.zfs.misc.arcstats.hash_chain_max"]
    hash_chains = Kstat["kstat.zfs.misc.arcstats.hash_chains"]
    hash_collisions = Kstat["kstat.zfs.misc.arcstats.hash_collisions"]
    hash_elements = Kstat["kstat.zfs.misc.arcstats.hash_elements"]
    hash_elements_max = Kstat["kstat.zfs.misc.arcstats.hash_elements_max"]

    output['arc_hash_break'] = {}
    output['arc_hash_break']['elements_max'] = fHits(hash_elements_max)
    output['arc_hash_break']['elements_current'] = {
        'per': fPerc(hash_elements, hash_elements_max),
        'num': fHits(hash_elements),
        }
    output['arc_hash_break']['collisions'] = fHits(hash_collisions)
    output['arc_hash_break']['chain_max'] = fHits(hash_chain_max)
    output['arc_hash_break']['chains'] = fHits(hash_chains)

    return output


def _arc_summary(Kstat):
    # ARC Sizing
    arc = get_arc_summary(Kstat)

    sys.stdout.write("ARC Summary: (%s)\n" % arc['health'])

    sys.stdout.write("\tMemory Throttle Count:\t\t\t%s\n" %
                     arc['memory_throttle_count'])
    sys.stdout.write("\n")

    # ARC Misc.
    sys.stdout.write("ARC Misc:\n")
    sys.stdout.write("\tDeleted:\t\t\t\t%s\n" % arc['arc_misc']['deleted'])
    sys.stdout.write("\tMutex Misses:\t\t\t\t%s\n" %
                     arc['arc_misc']['mutex_miss'])
    sys.stdout.write("\tEvict Skips:\t\t\t\t%s\n" %
                     arc['arc_misc']['mutex_miss'])
    sys.stdout.write("\n")

    # ARC Sizing
    sys.stdout.write("ARC Size:\t\t\t\t%s\t%s\n" % (
        arc['arc_sizing']['arc_size']['per'],
        arc['arc_sizing']['arc_size']['num']
        )
    )
    sys.stdout.write("\tTarget Size: (Adaptive)\t\t%s\t%s\n" % (
        arc['arc_sizing']['target_size']['per'],
        arc['arc_sizing']['target_size']['num'],
        )
    )

    sys.stdout.write("\tMin Size (Hard Limit):\t\t%s\t%s\n" % (
        arc['arc_sizing']['target_min_size']['per'],
        arc['arc_sizing']['target_min_size']['num'],
        )
    )

    sys.stdout.write("\tMax Size (High Water):\t\t%d:1\t%s\n" % (
        arc['arc_sizing']['target_max_size']['ratio'],
        arc['arc_sizing']['target_max_size']['num'],
        )
    )

    sys.stdout.write("\nARC Size Breakdown:\n")
    sys.stdout.write("\tRecently Used Cache Size:\t%s\t%s\n" % (
        arc['arc_size_break']['recently_used_cache_size']['per'],
        arc['arc_size_break']['recently_used_cache_size']['num'],
        )
    )
    sys.stdout.write("\tFrequently Used Cache Size:\t%s\t%s\n" % (
        arc['arc_size_break']['frequently_used_cache_size']['per'],
        arc['arc_size_break']['frequently_used_cache_size']['num'],
        )
    )

    sys.stdout.write("\n")

    # ARC Hash Breakdown
    sys.stdout.write("ARC Hash Breakdown:\n")
    sys.stdout.write("\tElements Max:\t\t\t\t%s\n" %
                     arc['arc_hash_break']['elements_max'])
    sys.stdout.write("\tElements Current:\t\t%s\t%s\n" % (
        arc['arc_hash_break']['elements_current']['per'],
        arc['arc_hash_break']['elements_current']['num'],
        )
    )
    sys.stdout.write("\tCollisions:\t\t\t\t%s\n" %
                     arc['arc_hash_break']['collisions'])
    sys.stdout.write("\tChain Max:\t\t\t\t%s\n" %
                     arc['arc_hash_break']['chain_max'])
    sys.stdout.write("\tChains:\t\t\t\t\t%s\n" %
                     arc['arc_hash_break']['chains'])


def get_arc_efficiency(Kstat):
    output = {}

    arc_hits = Kstat["kstat.zfs.misc.arcstats.hits"]
    arc_misses = Kstat["kstat.zfs.misc.arcstats.misses"]
    demand_data_hits = Kstat["kstat.zfs.misc.arcstats.demand_data_hits"]
    demand_data_misses = Kstat["kstat.zfs.misc.arcstats.demand_data_misses"]
    demand_metadata_hits = Kstat[
        "kstat.zfs.misc.arcstats.demand_metadata_hits"
        ]
    demand_metadata_misses = Kstat[
        "kstat.zfs.misc.arcstats.demand_metadata_misses"
        ]
    mfu_ghost_hits = Kstat["kstat.zfs.misc.arcstats.mfu_ghost_hits"]
    mfu_hits = Kstat["kstat.zfs.misc.arcstats.mfu_hits"]
    mru_ghost_hits = Kstat["kstat.zfs.misc.arcstats.mru_ghost_hits"]
    mru_hits = Kstat["kstat.zfs.misc.arcstats.mru_hits"]
    prefetch_data_hits = Kstat["kstat.zfs.misc.arcstats.prefetch_data_hits"]
    prefetch_data_misses = Kstat[
        "kstat.zfs.misc.arcstats.prefetch_data_misses"
        ]
    prefetch_metadata_hits = Kstat[
        "kstat.zfs.misc.arcstats.prefetch_metadata_hits"
        ]
    prefetch_metadata_misses = Kstat[
        "kstat.zfs.misc.arcstats.prefetch_metadata_misses"
        ]

    anon_hits = arc_hits - (
        mfu_hits + mru_hits + mfu_ghost_hits + mru_ghost_hits
        )
    arc_accesses_total = (arc_hits + arc_misses)
    demand_data_total = (demand_data_hits + demand_data_misses)
    prefetch_data_total = (prefetch_data_hits + prefetch_data_misses)
    real_hits = (mfu_hits + mru_hits)

    output["total_accesses"] = fHits(arc_accesses_total)
    output["cache_hit_ratio"] = {
        'per': fPerc(arc_hits, arc_accesses_total),
        'num': fHits(arc_hits),
    }
    output["cache_miss_ratio"] = {
        'per': fPerc(arc_misses, arc_accesses_total),
        'num': fHits(arc_misses),
    }
    output["actual_hit_ratio"] = {
        'per': fPerc(real_hits, arc_accesses_total),
        'num': fHits(real_hits),
    }
    output["data_demand_efficiency"] = {
        'per': fPerc(demand_data_hits, demand_data_total),
        'num': fHits(demand_data_total),
    }

    if prefetch_data_total > 0:
        output["data_prefetch_efficiency"] = {
            'per': fPerc(prefetch_data_hits, prefetch_data_total),
            'num': fHits(prefetch_data_total),
        }

    if anon_hits > 0:
        output["cache_hits_by_cache_list"] = {}
        output["cache_hits_by_cache_list"]["anonymously_used"] = {
            'per': fPerc(anon_hits, arc_hits),
            'num': fHits(anon_hits),
        }

    output["most_recently_used"] = {
        'per': fPerc(mru_hits, arc_hits),
        'num': fHits(mru_hits),
    }
    output["most_frequently_used"] = {
        'per': fPerc(mfu_hits, arc_hits),
        'num': fHits(mfu_hits),
    }
    output["most_recently_used_ghost"] = {
        'per': fPerc(mru_ghost_hits, arc_hits),
        'num': fHits(mru_ghost_hits),
    }
    output["most_frequently_used_ghost"] = {
        'per': fPerc(mfu_ghost_hits, arc_hits),
        'num': fHits(mfu_ghost_hits),
    }

    output["cache_hits_by_data_type"] = {}
    output["cache_hits_by_data_type"]["demand_data"] = {
        'per': fPerc(demand_data_hits, arc_hits),
        'num': fHits(demand_data_hits),
    }
    output["cache_hits_by_data_type"]["prefetch_data"] = {
        'per': fPerc(prefetch_data_hits, arc_hits),
        'num': fHits(prefetch_data_hits),
    }
    output["cache_hits_by_data_type"]["demand_metadata"] = {
        'per': fPerc(demand_metadata_hits, arc_hits),
        'num': fHits(demand_metadata_hits),
    }
    output["cache_hits_by_data_type"]["prefetch_metadata"] = {
        'per': fPerc(prefetch_metadata_hits, arc_hits),
        'num': fHits(prefetch_metadata_hits),
    }

    output["cache_misses_by_data_type"] = {}
    output["cache_misses_by_data_type"]["demand_data"] = {
        'per': fPerc(demand_data_misses, arc_misses),
        'num': fHits(demand_data_misses),
    }
    output["cache_misses_by_data_type"]["prefetch_data"] = {
        'per': fPerc(prefetch_data_misses, arc_misses),
        'num': fHits(prefetch_data_misses),
    }
    output["cache_misses_by_data_type"]["demand_metadata"] = {
        'per': fPerc(demand_metadata_misses, arc_misses),
        'num': fHits(demand_metadata_misses),
    }
    output["cache_misses_by_data_type"]["prefetch_metadata"] = {
        'per': fPerc(prefetch_metadata_misses, arc_misses),
        'num': fHits(prefetch_metadata_misses),
    }

    return output


def _arc_efficiency(Kstat):
    arc = get_arc_efficiency(Kstat)

    sys.stdout.write("ARC Total accesses:\t\t\t\t\t%s\n" %
                     arc['total_accesses'])
    sys.stdout.write("\tCache Hit Ratio:\t\t%s\t%s\n" % (
        arc['cache_hit_ratio']['per'],
        arc['cache_hit_ratio']['num'],
        )
    )
    sys.stdout.write("\tCache Miss Ratio:\t\t%s\t%s\n" % (
        arc['cache_miss_ratio']['per'],
        arc['cache_miss_ratio']['num'],
        )
    )

    sys.stdout.write("\tActual Hit Ratio:\t\t%s\t%s\n" % (
        arc['actual_hit_ratio']['per'],
        arc['actual_hit_ratio']['num'],
        )
    )

    sys.stdout.write("\n")
    sys.stdout.write("\tData Demand Efficiency:\t\t%s\t%s\n" % (
        arc['data_demand_efficiency']['per'],
        arc['data_demand_efficiency']['num'],
        )
    )

    if 'data_prefetch_efficiency' in arc:
        sys.stdout.write("\tData Prefetch Efficiency:\t%s\t%s\n" % (
            arc['data_prefetch_efficiency']['per'],
            arc['data_prefetch_efficiency']['num'],
            )
        )
    sys.stdout.write("\n")

    sys.stdout.write("\tCACHE HITS BY CACHE LIST:\n")
    if 'cache_hits_by_cache_list' in arc:
        sys.stdout.write("\t  Anonymously Used:\t\t%s\t%s\n" % (
            arc['cache_hits_by_cache_list']['anonymously_used']['per'],
            arc['cache_hits_by_cache_list']['anonymously_used']['num'],
            )
        )
    sys.stdout.write("\t  Most Recently Used:\t\t%s\t%s\n" % (
        arc['most_recently_used']['per'],
        arc['most_recently_used']['num'],
        )
    )
    sys.stdout.write("\t  Most Frequently Used:\t\t%s\t%s\n" % (
        arc['most_frequently_used']['per'],
        arc['most_frequently_used']['num'],
        )
    )
    sys.stdout.write("\t  Most Recently Used Ghost:\t%s\t%s\n" % (
        arc['most_recently_used_ghost']['per'],
        arc['most_recently_used_ghost']['num'],
        )
    )
    sys.stdout.write("\t  Most Frequently Used Ghost:\t%s\t%s\n" % (
        arc['most_frequently_used_ghost']['per'],
        arc['most_frequently_used_ghost']['num'],
        )
    )

    sys.stdout.write("\n\tCACHE HITS BY DATA TYPE:\n")
    sys.stdout.write("\t  Demand Data:\t\t\t%s\t%s\n" % (
        arc["cache_hits_by_data_type"]['demand_data']['per'],
        arc["cache_hits_by_data_type"]['demand_data']['num'],
        )
    )
    sys.stdout.write("\t  Prefetch Data:\t\t%s\t%s\n" % (
        arc["cache_hits_by_data_type"]['prefetch_data']['per'],
        arc["cache_hits_by_data_type"]['prefetch_data']['num'],
        )
    )
    sys.stdout.write("\t  Demand Metadata:\t\t%s\t%s\n" % (
        arc["cache_hits_by_data_type"]['demand_metadata']['per'],
        arc["cache_hits_by_data_type"]['demand_metadata']['num'],
        )
    )
    sys.stdout.write("\t  Prefetch Metadata:\t\t%s\t%s\n" % (
        arc["cache_hits_by_data_type"]['prefetch_metadata']['per'],
        arc["cache_hits_by_data_type"]['prefetch_metadata']['num'],
        )
    )

    sys.stdout.write("\n\tCACHE MISSES BY DATA TYPE:\n")
    sys.stdout.write("\t  Demand Data:\t\t\t%s\t%s\n" % (
        arc["cache_misses_by_data_type"]['demand_data']['per'],
        arc["cache_misses_by_data_type"]['demand_data']['num'],
        )
    )
    sys.stdout.write("\t  Prefetch Data:\t\t%s\t%s\n" % (
        arc["cache_misses_by_data_type"]['prefetch_data']['per'],
        arc["cache_misses_by_data_type"]['prefetch_data']['num'],
        )
    )
    sys.stdout.write("\t  Demand Metadata:\t\t%s\t%s\n" % (
        arc["cache_misses_by_data_type"]['demand_metadata']['per'],
        arc["cache_misses_by_data_type"]['demand_metadata']['num'],
        )
    )
    sys.stdout.write("\t  Prefetch Metadata:\t\t%s\t%s\n" % (
        arc["cache_misses_by_data_type"]['prefetch_metadata']['per'],
        arc["cache_misses_by_data_type"]['prefetch_metadata']['num'],
        )
    )


def get_l2arc_summary(Kstat):
    output = {}

    l2_abort_lowmem = Kstat["kstat.zfs.misc.arcstats.l2_abort_lowmem"]
    l2_cksum_bad = Kstat["kstat.zfs.misc.arcstats.l2_cksum_bad"]
    l2_evict_lock_retry = Kstat["kstat.zfs.misc.arcstats.l2_evict_lock_retry"]
    l2_evict_reading = Kstat["kstat.zfs.misc.arcstats.l2_evict_reading"]
    l2_feeds = Kstat["kstat.zfs.misc.arcstats.l2_feeds"]
    l2_free_on_write = Kstat["kstat.zfs.misc.arcstats.l2_free_on_write"]
    l2_hdr_size = Kstat["kstat.zfs.misc.arcstats.l2_hdr_size"]
    l2_hits = Kstat["kstat.zfs.misc.arcstats.l2_hits"]
    l2_io_error = Kstat["kstat.zfs.misc.arcstats.l2_io_error"]
    l2_misses = Kstat["kstat.zfs.misc.arcstats.l2_misses"]
    l2_rw_clash = Kstat["kstat.zfs.misc.arcstats.l2_rw_clash"]
    l2_size = Kstat["kstat.zfs.misc.arcstats.l2_size"]
    l2_asize = Kstat["kstat.zfs.misc.arcstats.l2_asize"]
    l2_writes_done = Kstat["kstat.zfs.misc.arcstats.l2_writes_done"]
    l2_writes_error = Kstat["kstat.zfs.misc.arcstats.l2_writes_error"]
    l2_writes_sent = Kstat["kstat.zfs.misc.arcstats.l2_writes_sent"]

    l2_access_total = (l2_hits + l2_misses)
    output['l2_health_count'] = (l2_writes_error + l2_cksum_bad + l2_io_error)

    output['l2_access_total'] = l2_access_total
    output['l2_size'] = l2_size
    output['l2_asize'] = l2_asize

    if l2_size > 0 and l2_access_total > 0:

        if output['l2_health_count'] > 0:
            output["health"] = "DEGRADED"
        else:
            output["health"] = "HEALTHY"

        output["low_memory_aborts"] = fHits(l2_abort_lowmem)
        output["free_on_write"] = fHits(l2_free_on_write)
        output["rw_clashes"] = fHits(l2_rw_clash)
        output["bad_checksums"] = fHits(l2_cksum_bad)
        output["io_errors"] = fHits(l2_io_error)

        output["l2_arc_size"] = {}
        output["l2_arc_size"]["adative"] = fBytes(l2_size)
        output["l2_arc_size"]["actual"] = {
            'per': fPerc(l2_asize, l2_size),
            'num': fBytes(l2_asize)
            }
        output["l2_arc_size"]["head_size"] = {
            'per': fPerc(l2_hdr_size, l2_size),
            'num': fBytes(l2_hdr_size),
        }

        output["l2_arc_evicts"] = {}
        output["l2_arc_evicts"]['lock_retries'] = fHits(l2_evict_lock_retry)
        output["l2_arc_evicts"]['reading'] = fHits(l2_evict_reading)

        output['l2_arc_breakdown'] = {}
        output['l2_arc_breakdown']['value'] = fHits(l2_access_total)
        output['l2_arc_breakdown']['hit_ratio'] = {
            'per': fPerc(l2_hits, l2_access_total),
            'num': fHits(l2_hits),
        }
        output['l2_arc_breakdown']['miss_ratio'] = {
            'per': fPerc(l2_misses, l2_access_total),
            'num': fHits(l2_misses),
        }
        output['l2_arc_breakdown']['feeds'] = fHits(l2_feeds)

        output['l2_arc_buffer'] = {}

        output['l2_arc_writes'] = {}
        output['l2_writes_done'] = l2_writes_done
        output['l2_writes_sent'] = l2_writes_sent
        if l2_writes_done != l2_writes_sent:
            output['l2_arc_writes']['writes_sent'] = {
                'value': "FAULTED",
                'num': fHits(l2_writes_sent),
            }
            output['l2_arc_writes']['done_ratio'] = {
                'per': fPerc(l2_writes_done, l2_writes_sent),
                'num': fHits(l2_writes_done),
            }
            output['l2_arc_writes']['error_ratio'] = {
                'per': fPerc(l2_writes_error, l2_writes_sent),
                'num': fHits(l2_writes_error),
            }
        else:
            output['l2_arc_writes']['writes_sent'] = {
                'per': fPerc(100),
                'num': fHits(l2_writes_sent),
            }

    return output


def _l2arc_summary(Kstat):

    arc = get_l2arc_summary(Kstat)

    if arc['l2_size'] > 0 and arc['l2_access_total'] > 0:
        sys.stdout.write("L2 ARC Summary: ")
        if arc['l2_health_count'] > 0:
            sys.stdout.write("(DEGRADED)\n")
        else:
            sys.stdout.write("(HEALTHY)\n")
        sys.stdout.write("\tLow Memory Aborts:\t\t\t%s\n" %
                         arc['low_memory_aborts'])
        sys.stdout.write("\tFree on Write:\t\t\t\t%s\n" % arc['free_on_write'])
        sys.stdout.write("\tR/W Clashes:\t\t\t\t%s\n" % arc['rw_clashes'])
        sys.stdout.write("\tBad Checksums:\t\t\t\t%s\n" % arc['bad_checksums'])
        sys.stdout.write("\tIO Errors:\t\t\t\t%s\n" % arc['io_errors'])
        sys.stdout.write("\n")

        sys.stdout.write("L2 ARC Size: (Adaptive)\t\t\t\t%s\n" %
                         arc["l2_arc_size"]["adative"])
        sys.stdout.write("\tCompressed:\t\t\t%s\t%s\n" % (
            arc["l2_arc_size"]["actual"]["per"],
            arc["l2_arc_size"]["actual"]["num"],
            )
        )
        sys.stdout.write("\tHeader Size:\t\t\t%s\t%s\n" % (
            arc["l2_arc_size"]["head_size"]["per"],
            arc["l2_arc_size"]["head_size"]["num"],
            )
        )
        sys.stdout.write("\n")

        if arc["l2_arc_evicts"]['lock_retries'] != '0' or \
           arc["l2_arc_evicts"]["reading"] != '0':
            sys.stdout.write("L2 ARC Evicts:\n")
            sys.stdout.write("\tLock Retries:\t\t\t\t%s\n" %
                             arc["l2_arc_evicts"]['lock_retries'])
            sys.stdout.write("\tUpon Reading:\t\t\t\t%s\n" %
                             arc["l2_arc_evicts"]["reading"])
            sys.stdout.write("\n")

        sys.stdout.write("L2 ARC Breakdown:\t\t\t\t%s\n" %
                         arc['l2_arc_breakdown']['value'])
        sys.stdout.write("\tHit Ratio:\t\t\t%s\t%s\n" % (
            arc['l2_arc_breakdown']['hit_ratio']['per'],
            arc['l2_arc_breakdown']['hit_ratio']['num'],
            )
        )

        sys.stdout.write("\tMiss Ratio:\t\t\t%s\t%s\n" % (
            arc['l2_arc_breakdown']['miss_ratio']['per'],
            arc['l2_arc_breakdown']['miss_ratio']['num'],
            )
        )

        sys.stdout.write("\tFeeds:\t\t\t\t\t%s\n" %
                         arc['l2_arc_breakdown']['feeds'])
        sys.stdout.write("\n")

        sys.stdout.write("L2 ARC Writes:\n")
        if arc['l2_writes_done'] != arc['l2_writes_sent']:
            sys.stdout.write("\tWrites Sent: (%s)\t\t\t\t%s\n" % (
                arc['l2_arc_writes']['writes_sent']['value'],
                arc['l2_arc_writes']['writes_sent']['num'],
                )
            )
            sys.stdout.write("\t  Done Ratio:\t\t\t%s\t%s\n" % (
                arc['l2_arc_writes']['done_ratio']['per'],
                arc['l2_arc_writes']['done_ratio']['num'],
                )
            )
            sys.stdout.write("\t  Error Ratio:\t\t\t%s\t%s\n" % (
                arc['l2_arc_writes']['error_ratio']['per'],
                arc['l2_arc_writes']['error_ratio']['num'],
                )
            )
        else:
            sys.stdout.write("\tWrites Sent:\t\t\t%s\t%s\n" % (
                arc['l2_arc_writes']['writes_sent']['per'],
                arc['l2_arc_writes']['writes_sent']['num'],
                )
            )


def get_dmu_summary(Kstat):
    output = {}

    zfetch_hits = Kstat["kstat.zfs.misc.zfetchstats.hits"]
    zfetch_misses = Kstat["kstat.zfs.misc.zfetchstats.misses"]

    zfetch_access_total = (zfetch_hits + zfetch_misses)
    output['zfetch_access_total'] = zfetch_access_total

    if zfetch_access_total > 0:
        output['dmu'] = {}
        output['dmu']['efficiency'] = {}
        output['dmu']['efficiency']['value'] = fHits(zfetch_access_total)
        output['dmu']['efficiency']['hit_ratio'] = {
            'per': fPerc(zfetch_hits, zfetch_access_total),
            'num': fHits(zfetch_hits),
        }
        output['dmu']['efficiency']['miss_ratio'] = {
            'per': fPerc(zfetch_misses, zfetch_access_total),
            'num': fHits(zfetch_misses),
        }

    return output


def _dmu_summary(Kstat):

    arc = get_dmu_summary(Kstat)

    if arc['zfetch_access_total'] > 0:
        sys.stdout.write("DMU Prefetch Efficiency:\t\t\t\t\t%s\n" %
                         arc['dmu']['efficiency']['value'])
        sys.stdout.write("\tHit Ratio:\t\t\t%s\t%s\n" % (
            arc['dmu']['efficiency']['hit_ratio']['per'],
            arc['dmu']['efficiency']['hit_ratio']['num'],
            )
        )
        sys.stdout.write("\tMiss Ratio:\t\t\t%s\t%s\n" % (
            arc['dmu']['efficiency']['miss_ratio']['per'],
            arc['dmu']['efficiency']['miss_ratio']['num'],
            )
        )

        sys.stdout.write("\n")


def get_vdev_summary(Kstat):
    output = {}

    vdev_cache_delegations = \
        Kstat["kstat.zfs.misc.vdev_cache_stats.delegations"]
    vdev_cache_misses = Kstat["kstat.zfs.misc.vdev_cache_stats.misses"]
    vdev_cache_hits = Kstat["kstat.zfs.misc.vdev_cache_stats.hits"]
    vdev_cache_total = (vdev_cache_misses + vdev_cache_hits +
                        vdev_cache_delegations)

    output['vdev_cache_total'] = vdev_cache_total

    if vdev_cache_total > 0:
        output['summary'] = fHits(vdev_cache_total)
        output['hit_ratio'] = {
            'per': fPerc(vdev_cache_hits, vdev_cache_total),
            'num': fHits(vdev_cache_hits),
        }
        output['miss_ratio'] = {
            'per': fPerc(vdev_cache_misses, vdev_cache_total),
            'num': fHits(vdev_cache_misses),
        }
        output['delegations'] = {
            'per': fPerc(vdev_cache_delegations, vdev_cache_total),
            'num': fHits(vdev_cache_delegations),
        }

    return output


def _vdev_summary(Kstat):
    arc = get_vdev_summary(Kstat)

    if arc['vdev_cache_total'] > 0:
        sys.stdout.write("VDEV Cache Summary:\t\t\t\t%s\n" % arc['summary'])
        sys.stdout.write("\tHit Ratio:\t\t\t%s\t%s\n" % (
            arc['hit_ratio']['per'],
            arc['hit_ratio']['num'],
        ))
        sys.stdout.write("\tMiss Ratio:\t\t\t%s\t%s\n" % (
            arc['miss_ratio']['per'],
            arc['miss_ratio']['num'],
        ))
        sys.stdout.write("\tDelegations:\t\t\t%s\t%s\n" % (
            arc['delegations']['per'],
            arc['delegations']['num'],
        ))


def _tunable_summary(Kstat):
    global show_tunable_descriptions
    global alternate_tunable_layout

    names = listdir("/sys/module/zfs/parameters/")

    values = {}
    for name in names:
        with open("/sys/module/zfs/parameters/" + name) as f:
            value = f.read()
        values[name] = value.strip()

    descriptions = {}

    if show_tunable_descriptions:
        try:
            command = ["/sbin/modinfo", "zfs", "-0"]
            p = Popen(command, stdin=PIPE, stdout=PIPE,
                      stderr=PIPE, shell=False, close_fds=True)
            p.wait()

            description_list = p.communicate()[0].strip().split('\0')

            if p.returncode == 0:
                for tunable in description_list:
                    if tunable[0:5] == 'parm:':
                        tunable = tunable[5:].strip()
                        name, description = tunable.split(':', 1)
                        if not description:
                            description = "Description unavailable"
                        descriptions[name] = description
            else:
                sys.stderr.write("%s: '%s' exited with code %i\n" %
                                 (sys.argv[0], command[0], p.returncode))
                sys.stderr.write("Tunable descriptions will be disabled.\n")
        except OSError as e:
            sys.stderr.write("%s: Cannot run '%s': %s\n" %
                             (sys.argv[0], command[0], e.strerror))
            sys.stderr.write("Tunable descriptions will be disabled.\n")

    sys.stdout.write("ZFS Tunable:\n")
    for name in names:
        if not name:
            continue

        format = "\t%-50s%s\n"
        if alternate_tunable_layout:
            format = "\t%s=%s\n"

        if show_tunable_descriptions and name in descriptions:
            sys.stdout.write("\t# %s\n" % descriptions[name])

        sys.stdout.write(format % (name, values[name]))


unSub = [
    _arc_summary,
    _arc_efficiency,
    _l2arc_summary,
    _dmu_summary,
    _vdev_summary,
    _tunable_summary
]


def zfs_header():
    daydate = time.strftime("%a %b %d %H:%M:%S %Y")

    div1()
    sys.stdout.write("ZFS Subsystem Report\t\t\t\t%s" % daydate)
    div2()


def usage():
    sys.stdout.write("Usage: arc_summary.py [-h] [-a] [-d] [-p PAGE]\n\n")
    sys.stdout.write("\t -h, --help           : "
                     "Print this help message and exit\n")
    sys.stdout.write("\t -a, --alternate      : "
                     "Show an alternate sysctl layout\n")
    sys.stdout.write("\t -d, --description    : "
                     "Show the sysctl descriptions\n")
    sys.stdout.write("\t -p PAGE, --page=PAGE : "
                     "Select a single output page to display,\n")
    sys.stdout.write("\t                        "
                     "should be an integer between 1 and " +
                     str(len(unSub)) + "\n\n")
    sys.stdout.write("Examples:\n")
    sys.stdout.write("\tarc_summary.py -a\n")
    sys.stdout.write("\tarc_summary.py -p 4\n")
    sys.stdout.write("\tarc_summary.py -ad\n")
    sys.stdout.write("\tarc_summary.py --page=2\n")


def main():
    global show_tunable_descriptions
    global alternate_tunable_layout

    opts, args = getopt.getopt(
        sys.argv[1:], "adp:h", ["alternate", "description", "page=", "help"]
    )

    args = {}
    for opt, arg in opts:
        if opt in ('-a', '--alternate'):
            args['a'] = True
        if opt in ('-d', '--description'):
            args['d'] = True
        if opt in ('-p', '--page'):
            args['p'] = arg
        if opt in ('-h', '--help'):
            usage()
            sys.exit()

    Kstat = get_Kstat()

    alternate_tunable_layout = 'a' in args
    show_tunable_descriptions = 'd' in args

    pages = []

    if 'p' in args:
        try:
            pages.append(unSub[int(args['p']) - 1])
        except IndexError:
            sys.stderr.write('the argument to -p must be between 1 and ' +
                             str(len(unSub)) + '\n')
            sys.exit()
    else:
        pages = unSub

    zfs_header()
    for page in pages:
        page(Kstat)
        div2()


if __name__ == '__main__':
    main()