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Add zfs_arc_meta_limit_percent tunable

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ARC will evict meta buffers that exceed the arc_meta_limit. Before a further
investigating on whether we should take special protection on meta buffers,
this tunable make arc_meta_limit adjustable for different workloads.

People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko,
so some range check is added to guarantee a suitable arc_meta_limit.

Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style
tunable as well.

Signed-off-by: GeLiXin <ge.lixin@zte.com.cn>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4957
This commit is contained in:
GeLiXin
2016-08-11 11:15:37 +08:00
committed by Brian Behlendorf
parent 3e635ac15c
commit 9907cc1cc8
2 changed files with 71 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/zfs/arc.c
Regular → Executable
+34 -6
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@@ -239,6 +239,17 @@ int zfs_arc_p_min_shift = 0;
int zfs_disable_dup_eviction = 0;
int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
/*
* ARC will evict meta buffers that exceed arc_meta_limit. This
* tunable make arc_meta_limit adjustable for different workloads.
*/
unsigned long zfs_arc_meta_limit_percent = 75;
/*
* Percentage that can be consumed by dnodes of ARC meta buffers.
*/
unsigned long zfs_arc_dnode_limit_percent = 10;
/*
* These tunables are Linux specific
*/
@@ -5357,6 +5368,7 @@ arc_state_multilist_index_func(multilist_t *ml, void *obj)
static void
arc_tuning_update(void)
{
uint64_t percent;
/* Valid range: 64M - <all physical memory> */
if ((zfs_arc_max) && (zfs_arc_max != arc_c_max) &&
(zfs_arc_max > 64 << 20) && (zfs_arc_max < ptob(physmem)) &&
@@ -5364,8 +5376,11 @@ arc_tuning_update(void)
arc_c_max = zfs_arc_max;
arc_c = arc_c_max;
arc_p = (arc_c >> 1);
arc_meta_limit = (3 * arc_c_max) / 4;
arc_dnode_limit = arc_meta_limit / 10;
/* Valid range of arc_meta_limit: arc_meta_min - arc_c_max */
percent = MIN(zfs_arc_meta_limit_percent, 100);
arc_meta_limit = MAX(arc_meta_min, (percent * arc_c_max) / 100);
percent = MIN(zfs_arc_dnode_limit_percent, 100);
arc_dnode_limit = (percent * arc_meta_limit) / 100;
}
/* Valid range: 32M - <arc_c_max> */
@@ -5437,6 +5452,7 @@ arc_init(void)
#else
uint64_t allmem = (physmem * PAGESIZE) / 2;
#endif
uint64_t percent;
mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
@@ -5493,10 +5509,14 @@ arc_init(void)
arc_meta_min = 1ULL << SPA_MAXBLOCKSHIFT;
/* Initialize maximum observed usage to zero */
arc_meta_max = 0;
/* Set limit to 3/4 of arc_c_max with a floor of arc_meta_min */
arc_meta_limit = MAX((3 * arc_c_max) / 4, arc_meta_min);
/* Default dnode limit is 10% of overall meta limit */
arc_dnode_limit = arc_meta_limit / 10;
/*
* Set arc_meta_limit to a percent of arc_c_max with a floor of
* arc_meta_min, and a ceiling of arc_c_max.
*/
percent = MIN(zfs_arc_meta_limit_percent, 100);
arc_meta_limit = MAX(arc_meta_min, (percent * arc_c_max) / 100);
percent = MIN(zfs_arc_dnode_limit_percent, 100);
arc_dnode_limit = (percent * arc_meta_limit) / 100;
/* Apply user specified tunings */
arc_tuning_update();
@@ -7169,6 +7189,10 @@ MODULE_PARM_DESC(zfs_arc_max, "Max arc size");
module_param(zfs_arc_meta_limit, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size");
module_param(zfs_arc_meta_limit_percent, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_meta_limit_percent,
"Percent of arc size for arc meta limit");
module_param(zfs_arc_meta_min, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_meta_min, "Min arc metadata");
@@ -7253,6 +7277,10 @@ MODULE_PARM_DESC(zfs_arc_sys_free, "System free memory target size in bytes");
module_param(zfs_arc_dnode_limit, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_dnode_limit, "Minimum bytes of dnodes in arc");
module_param(zfs_arc_dnode_limit_percent, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_dnode_limit_percent,
"Percent of ARC meta buffers for dnodes");
module_param(zfs_arc_dnode_reduce_percent, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_dnode_reduce_percent,
"Percentage of excess dnodes to try to unpin");