Fix for ARC sysctls ignored at runtime

This change leverage module_param_call() to run arc_tuning_update()
immediately after the ARC tunable has been updated as suggested in
cffa8372 code review.

A simple test case is added to the ZFS Test Suite to prevent future
regressions in functionality.

Reviewed-by: Matt Macy <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: loli10K <[email protected]>
Closes #9487  
Closes #9489 

10 files changed, 178 insertions, 42 deletions

diff --git a/include/os/linux/kernel/linux/mod_compat.h b/include/os/linux/kernel/linux/mod_compat.h
index 1f19f4b40..5579cb5bf 100644
--- a/include/os/linux/kernel/linux/mod_compat.h
+++ b/include/os/linux/kernel/linux/mod_compat.h
@@ -76,26 +76,26 @@ enum scope_prefix_types {
 /*
  * Declare a module parameter / sysctl node
  *
- * scope_prefix the part of the the sysctl / sysfs tree the node resides under
+ * "scope_prefix" the part of the the sysctl / sysfs tree the node resides under
  *   (currently a no-op on Linux)
- * name_prefix the part of the variable name that will be excluded from the
+ * "name_prefix" the part of the variable name that will be excluded from the
  *   exported names on platforms with a hierarchical namespace
- * name the part of the variable that will be exposed on platforms with a
+ * "name" the part of the variable that will be exposed on platforms with a
  *    hierarchical namespace, or as name_prefix ## name on Linux
- * type the variable type
- * perm the permissions (read/write or read only)
- * desc a brief description of the option
+ * "type" the variable type
+ * "perm" the permissions (read/write or read only)
+ * "desc" a brief description of the option
  *
  * Examples:
  * ZFS_MODULE_PARAM(zfs_vdev_mirror, zfs_vdev_mirror_, rotating_inc, UINT,
- *	 ZMOD_RW, "Rotating media load increment for non-seeking I/O's");
+ * 	ZMOD_RW, "Rotating media load increment for non-seeking I/O's");
  * on FreeBSD:
  *   vfs.zfs.vdev.mirror.rotating_inc
  * on Linux:
  *   zfs_vdev_mirror_rotating_inc
  *
- * *ZFS_MODULE_PARAM(zfs, , dmu_prefetch_max, UINT, ZMOD_RW,
- *	"Limit one prefetch call to this size");
+ * ZFS_MODULE_PARAM(zfs, , dmu_prefetch_max, UINT, ZMOD_RW,
+ * 	"Limit one prefetch call to this size");
  * on FreeBSD:
  *   vfs.zfs.dmu_prefetch_max
  * on Linux:
@@ -108,5 +108,33 @@ enum scope_prefix_types {
 	MODULE_PARM_DESC(name_prefix ## name, desc)
 /* END CSTYLED */
 
+/*
+ * Declare a module parameter / sysctl node
+ *
+ * "scope_prefix" the part of the the sysctl / sysfs tree the node resides under
+ *   (currently a no-op on Linux)
+ * "name_prefix" the part of the variable name that will be excluded from the
+ *   exported names on platforms with a hierarchical namespace
+ * "name" the part of the variable that will be exposed on platforms with a
+ *    hierarchical namespace, or as name_prefix ## name on Linux
+ * "setfunc" setter function
+ * "getfunc" getter function
+ * "perm" the permissions (read/write or read only)
+ * "desc" a brief description of the option
+ *
+ * Examples:
+ * ZFS_MODULE_PARAM_CALL(zfs_spa, spa_, slop_shift, param_set_slop_shift,
+ * 	param_get_int, ZMOD_RW, "Reserved free space in pool");
+ * on FreeBSD:
+ *   vfs.zfs.spa_slop_shift
+ * on Linux:
+ *   spa_slop_shift
+ */
+/* BEGIN CSTYLED */
+#define ZFS_MODULE_PARAM_CALL(scope_prefix, name_prefix, name, setfunc, getfunc, perm, desc) \
+	CTASSERT_GLOBAL((sizeof (scope_prefix) == sizeof (enum scope_prefix_types))); \
+	module_param_call(name_prefix ## name, setfunc, getfunc, &name_prefix ## name, perm); \
+	MODULE_PARM_DESC(name_prefix ## name, desc)
+/* END CSTYLED */
 
 #endif	/* _MOD_COMPAT_H */
diff --git a/include/sys/arc_impl.h b/include/sys/arc_impl.h
index 28d430f04..8eeee54c9 100644
--- a/include/sys/arc_impl.h
+++ b/include/sys/arc_impl.h
@@ -611,6 +611,10 @@ extern void arc_prune_async(int64_t);
 extern int arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg);
 extern uint64_t arc_free_memory(void);
 extern int64_t arc_available_memory(void);
+extern void arc_tuning_update(void);
+
+extern int param_set_arc_long(const char *buf, zfs_kernel_param_t *kp);
+extern int param_set_arc_int(const char *buf, zfs_kernel_param_t *kp);
 
 #ifdef __cplusplus
 }
diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index a493c30dd..18d9b25a3 100644
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -198,7 +198,13 @@ extern int aok;
 /*
  * Tunables.
  */
+typedef struct zfs_kernel_param {
+	const char *name;	/* unused stub */
+} zfs_kernel_param_t;
+
 #define	ZFS_MODULE_PARAM(scope_prefix, name_prefix, name, type, perm, desc)
+#define	ZFS_MODULE_PARAM_CALL(scope_prefix, name_prefix, name, setfunc, \
+	getfunc, perm, desc)
 
 /*
  * Exported symbols
diff --git a/module/os/linux/zfs/arc_os.c b/module/os/linux/zfs/arc_os.c
index 696f671ab..c9db31096 100644
--- a/module/os/linux/zfs/arc_os.c
+++ b/module/os/linux/zfs/arc_os.c
@@ -357,6 +357,34 @@ arc_lowmem_fini(void)
 {
 	spl_unregister_shrinker(&arc_shrinker);
 }
+
+int
+param_set_arc_long(const char *buf, zfs_kernel_param_t *kp)
+{
+	int error;
+
+	error = param_set_long(buf, kp);
+	if (error < 0)
+		return (SET_ERROR(error));
+
+	arc_tuning_update();
+
+	return (0);
+}
+
+int
+param_set_arc_int(const char *buf, zfs_kernel_param_t *kp)
+{
+	int error;
+
+	error = param_set_int(buf, kp);
+	if (error < 0)
+		return (SET_ERROR(error));
+
+	arc_tuning_update();
+
+	return (0);
+}
 #else /* _KERNEL */
 int64_t
 arc_available_memory(void)
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index b1a9681dd..45211bc5c 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -24,6 +24,7 @@
  * Copyright (c) 2011, 2019 by Delphix. All rights reserved.
  * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
  * Copyright 2017 Nexenta Systems, Inc.  All rights reserved.
+ * Copyright (c) 2019, loli10K <[email protected]>. All rights reserved.
  */
 
 /*
@@ -814,7 +815,6 @@ static void arc_hdr_alloc_abd(arc_buf_hdr_t *, boolean_t);
 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
 static boolean_t arc_is_overflowing(void);
 static void arc_buf_watch(arc_buf_t *);
-static void arc_tuning_update(void);
 
 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
@@ -6873,10 +6873,12 @@ arc_state_multilist_index_func(multilist_t *ml, void *obj)
 
 /*
  * Called during module initialization and periodically thereafter to
- * apply reasonable changes to the exposed performance tunings.  Non-zero
- * zfs_* values which differ from the currently set values will be applied.
+ * apply reasonable changes to the exposed performance tunings.  Can also be
+ * called explicitly by param_set_arc_*() functions when ARC tunables are
+ * updated manually.  Non-zero zfs_* values which differ from the currently set
+ * values will be applied.
  */
-static void
+void
 arc_tuning_update(void)
 {
 	uint64_t allmem = arc_all_memory();
@@ -8694,20 +8696,21 @@ EXPORT_SYMBOL(arc_add_prune_callback);
 EXPORT_SYMBOL(arc_remove_prune_callback);
 
 /* BEGIN CSTYLED */
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, min, ULONG, ZMOD_RW,
-	"Min arc size");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min, param_set_arc_long,
+	param_get_long, ZMOD_RW, "Min arc size");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, max, ULONG, ZMOD_RW,
-	"Max arc size");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, max, param_set_arc_long,
+	param_get_long, ZMOD_RW, "Max arc size");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_limit, ULONG, ZMOD_RW,
-	"Metadata limit for arc size");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, meta_limit, param_set_arc_long,
+	param_get_long, ZMOD_RW, "Metadata limit for arc size");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_limit_percent, ULONG, ZMOD_RW,
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, meta_limit_percent,
+	param_set_arc_long, param_get_long, ZMOD_RW,
 	"Percent of arc size for arc meta limit");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_min, ULONG, ZMOD_RW,
-	"Min arc metadata");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, meta_min, param_set_arc_long,
+	param_get_long, ZMOD_RW, "Min arc metadata");
 
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_prune, INT, ZMOD_RW,
 	"Meta objects to scan for prune");
@@ -8718,20 +8721,20 @@ ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_adjust_restarts, INT, ZMOD_RW,
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, meta_strategy, INT, ZMOD_RW,
 	"Meta reclaim strategy");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, grow_retry, INT, ZMOD_RW,
-	"Seconds before growing arc size");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, grow_retry, param_set_arc_int,
+	param_get_int, ZMOD_RW, "Seconds before growing arc size");
 
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, p_dampener_disable, INT, ZMOD_RW,
 	"Disable arc_p adapt dampener");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, shrink_shift, INT, ZMOD_RW,
-	"log2(fraction of arc to reclaim)");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, shrink_shift, param_set_arc_int,
+	param_get_int, ZMOD_RW, "log2(fraction of arc to reclaim)");
 
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, pc_percent, UINT, ZMOD_RW,
 	"Percent of pagecache to reclaim arc to");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, p_min_shift, INT, ZMOD_RW,
-	"arc_c shift to calc min/max arc_p");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, p_min_shift, param_set_arc_int,
+	param_get_int, ZMOD_RW, "arc_c shift to calc min/max arc_p");
 
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, average_blocksize, INT, ZMOD_RD,
 	"Target average block size");
@@ -8739,10 +8742,11 @@ ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, average_blocksize, INT, ZMOD_RD,
 ZFS_MODULE_PARAM(zfs, zfs_, compressed_arc_enabled, INT, ZMOD_RW,
 	"Disable compressed arc buffers");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, min_prefetch_ms, INT, ZMOD_RW,
-	"Min life of prefetch block in ms");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min_prefetch_ms, param_set_arc_int,
+	param_get_int, ZMOD_RW, "Min life of prefetch block in ms");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, min_prescient_prefetch_ms, INT, ZMOD_RW,
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, min_prescient_prefetch_ms,
+	param_set_arc_int, param_get_int, ZMOD_RW,
 	"Min life of prescient prefetched block in ms");
 
 ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, write_max, ULONG, ZMOD_RW,
@@ -8772,16 +8776,17 @@ ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, feed_again, INT, ZMOD_RW,
 ZFS_MODULE_PARAM(zfs_l2arc, l2arc_, norw, INT, ZMOD_RW,
 	"No reads during writes");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, lotsfree_percent, INT, ZMOD_RW,
-	"System free memory I/O throttle in bytes");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, lotsfree_percent, param_set_arc_int,
+	param_get_int, ZMOD_RW, "System free memory I/O throttle in bytes");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, sys_free, ULONG, ZMOD_RW,
-	"System free memory target size in bytes");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, sys_free, param_set_arc_long,
+	param_get_long, ZMOD_RW, "System free memory target size in bytes");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, dnode_limit, ULONG, ZMOD_RW,
-	"Minimum bytes of dnodes in arc");
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, dnode_limit, param_set_arc_long,
+	param_get_long, ZMOD_RW, "Minimum bytes of dnodes in arc");
 
-ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, dnode_limit_percent, ULONG, ZMOD_RW,
+ZFS_MODULE_PARAM_CALL(zfs_arc, zfs_arc_, dnode_limit_percent,
+	param_set_arc_long, param_get_long, ZMOD_RW,
 	"Percent of ARC meta buffers for dnodes");
 
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, dnode_reduce_percent, ULONG, ZMOD_RW,
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index 78bf110b4..46279517d 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -26,6 +26,7 @@
  * Copyright 2013 Saso Kiselkov. All rights reserved.
  * Copyright (c) 2017 Datto Inc.
  * Copyright (c) 2017, Intel Corporation.
+ * Copyright (c) 2019, loli10K <[email protected]>. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -2920,9 +2921,8 @@ module_param_call(zfs_deadman_ziotime_ms, param_set_deadman_ziotime,
 MODULE_PARM_DESC(zfs_deadman_ziotime_ms,
 	"IO expiration time in milliseconds");
 
-module_param_call(spa_slop_shift, param_set_slop_shift, param_get_int,
-	&spa_slop_shift, 0644);
-MODULE_PARM_DESC(spa_slop_shift, "Reserved free space in pool");
+ZFS_MODULE_PARAM_CALL(zfs_spa, spa_, slop_shift, param_set_slop_shift,
+	param_get_int, ZMOD_RW, "Reserved free space in pool");
 
 module_param_call(zfs_deadman_failmode, param_set_deadman_failmode,
 	param_get_charp, &zfs_deadman_failmode, 0644);
diff --git a/tests/runfiles/linux.run b/tests/runfiles/linux.run
index 777588ac4..a134c8db8 100644
--- a/tests/runfiles/linux.run
+++ b/tests/runfiles/linux.run
@@ -25,7 +25,8 @@ tests = ['posix_001_pos', 'posix_002_pos', 'posix_003_pos']
 tags = ['functional', 'acl', 'posix']
 
 [tests/functional/arc:Linux]
-tests = ['dbufstats_001_pos', 'dbufstats_002_pos', 'dbufstats_003_pos']
+tests = ['dbufstats_001_pos', 'dbufstats_002_pos', 'dbufstats_003_pos',
+    'arcstats_runtime_tuning']
 tags = ['functional', 'arc']
 
 [tests/functional/atime:Linux]
diff --git a/tests/zfs-tests/tests/functional/arc/Makefile.am b/tests/zfs-tests/tests/functional/arc/Makefile.am
index 22704fa51..809d0346f 100644
--- a/tests/zfs-tests/tests/functional/arc/Makefile.am
+++ b/tests/zfs-tests/tests/functional/arc/Makefile.am
@@ -2,6 +2,7 @@ pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/arc
 dist_pkgdata_SCRIPTS = \
 	cleanup.ksh \
 	setup.ksh \
+	arcstats_runtime_tuning.ksh \
 	dbufstats_001_pos.ksh \
 	dbufstats_002_pos.ksh \
 	dbufstats_003_pos.ksh
diff --git a/tests/zfs-tests/tests/functional/arc/arcstats_runtime_tuning.ksh b/tests/zfs-tests/tests/functional/arc/arcstats_runtime_tuning.ksh
new file mode 100755
index 000000000..6d007aecf
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/arc/arcstats_runtime_tuning.ksh
@@ -0,0 +1,46 @@
+#!/bin/ksh -p
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright 2019, loli10K <[email protected]>. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/perf/perf.shlib
+
+function cleanup
+{
+	# Set tunables to their recorded actual size and then to their original
+	# value: this works for previously unconfigured tunables.
+	log_must set_tunable64 zfs_arc_min "$MINSIZE"
+	log_must set_tunable64 zfs_arc_min "$ZFS_ARC_MIN"
+	log_must set_tunable64 zfs_arc_max "$MAXSIZE"
+	log_must set_tunable64 zfs_arc_max "$ZFS_ARC_MAX"
+}
+
+log_onexit cleanup
+
+ZFS_ARC_MAX="$(get_tunable zfs_arc_max)"
+ZFS_ARC_MIN="$(get_tunable zfs_arc_min)"
+MINSIZE="$(get_min_arc_size)"
+MAXSIZE="$(get_max_arc_size)"
+
+log_assert "ARC tunables should be updated dynamically"
+
+for size in $((MAXSIZE/4)) $((MAXSIZE/3)) $((MAXSIZE/2)) $MAXSIZE; do
+	log_must set_tunable64 zfs_arc_max "$size"
+	log_must test "$(get_max_arc_size)" == "$size"
+	log_must set_tunable64 zfs_arc_min "$size"
+	log_must test "$(get_min_arc_size)" == "$size"
+done
+
+log_pass "ARC tunables can be updated dynamically"
diff --git a/tests/zfs-tests/tests/perf/perf.shlib b/tests/zfs-tests/tests/perf/perf.shlib
index 69e61e9fd..e2e84ca02 100644
--- a/tests/zfs-tests/tests/perf/perf.shlib
+++ b/tests/zfs-tests/tests/perf/perf.shlib
@@ -373,6 +373,23 @@ function get_directory
 	echo $directory
 }
 
+function get_min_arc_size
+{
+	if is_linux; then
+		typeset -l min_arc_size=`awk '$1 == "c_min" { print $3 }' \
+		    /proc/spl/kstat/zfs/arcstats`
+	else
+		typeset -l min_arc_size=$(dtrace -qn 'BEGIN {
+		    printf("%u\n", `arc_stats.arcstat_c_min.value.ui64);
+		    exit(0);
+		}')
+	fi
+
+	[[ $? -eq 0 ]] || log_fail "get_min_arc_size failed"
+
+	echo $min_arc_size
+}
+
 function get_max_arc_size
 {
 	if is_linux; then