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vdev_mirror: kstat observables for preferred vdev
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Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Gvozden Neskovic <[email protected]>
Closes #6461
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ironMann authored and behlendorf committed Aug 21, 2017
1 parent d6c6590 commit 551905d
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Showing 3 changed files with 82 additions and 6 deletions.
4 changes: 4 additions & 0 deletions include/sys/spa.h
Original file line number Diff line number Diff line change
Expand Up @@ -1034,6 +1034,10 @@ extern void spa_get_errlists(spa_t *spa, avl_tree_t *last, avl_tree_t *scrub);
extern void vdev_cache_stat_init(void);
extern void vdev_cache_stat_fini(void);

/* vdev mirror */
extern void vdev_mirror_stat_init(void);
extern void vdev_mirror_stat_fini(void);

/* Initialization and termination */
extern void spa_init(int flags);
extern void spa_fini(void);
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2 changes: 2 additions & 0 deletions module/zfs/spa_misc.c
Original file line number Diff line number Diff line change
Expand Up @@ -1897,6 +1897,7 @@ spa_init(int mode)
dmu_init();
zil_init();
vdev_cache_stat_init();
vdev_mirror_stat_init();
vdev_raidz_math_init();
vdev_file_init();
zfs_prop_init();
Expand All @@ -1916,6 +1917,7 @@ spa_fini(void)

vdev_file_fini();
vdev_cache_stat_fini();
vdev_mirror_stat_fini();
vdev_raidz_math_fini();
zil_fini();
dmu_fini();
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82 changes: 76 additions & 6 deletions module/zfs/vdev_mirror.c
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,65 @@
#include <sys/abd.h>
#include <sys/fs/zfs.h>

/*
* Vdev mirror kstats
*/
static kstat_t *mirror_ksp = NULL;

typedef struct mirror_stats {
kstat_named_t vdev_mirror_stat_rotating_linear;
kstat_named_t vdev_mirror_stat_rotating_offset;
kstat_named_t vdev_mirror_stat_rotating_seek;
kstat_named_t vdev_mirror_stat_non_rotating_linear;
kstat_named_t vdev_mirror_stat_non_rotating_seek;

kstat_named_t vdev_mirror_stat_preferred_found;
kstat_named_t vdev_mirror_stat_preferred_not_found;
} mirror_stats_t;

static mirror_stats_t mirror_stats = {
/* New I/O follows directly the last I/O */
{ "rotating_linear", KSTAT_DATA_UINT64 },
/* New I/O is within zfs_vdev_mirror_rotating_seek_offset of the last */
{ "rotating_offset", KSTAT_DATA_UINT64 },
/* New I/O requires random seek */
{ "rotating_seek", KSTAT_DATA_UINT64 },
/* New I/O follows directly the last I/O (nonrot) */
{ "non_rotating_linear", KSTAT_DATA_UINT64 },
/* New I/O requires random seek (nonrot) */
{ "non_rotating_seek", KSTAT_DATA_UINT64 },
/* Preferred child vdev found */
{ "preferred_found", KSTAT_DATA_UINT64 },
/* Preferred child vdev not found or equal load */
{ "preferred_not_found", KSTAT_DATA_UINT64 },

};

#define MIRROR_STAT(stat) (mirror_stats.stat.value.ui64)
#define MIRROR_INCR(stat, val) atomic_add_64(&MIRROR_STAT(stat), val)
#define MIRROR_BUMP(stat) MIRROR_INCR(stat, 1)

void
vdev_mirror_stat_init(void)
{
mirror_ksp = kstat_create("zfs", 0, "vdev_mirror_stats",
"misc", KSTAT_TYPE_NAMED,
sizeof (mirror_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
if (mirror_ksp != NULL) {
mirror_ksp->ks_data = &mirror_stats;
kstat_install(mirror_ksp);
}
}

void
vdev_mirror_stat_fini(void)
{
if (mirror_ksp != NULL) {
kstat_delete(mirror_ksp);
mirror_ksp = NULL;
}
}

/*
* Virtual device vector for mirroring.
*/
Expand Down Expand Up @@ -140,32 +199,40 @@ vdev_mirror_load(mirror_map_t *mm, vdev_t *vd, uint64_t zio_offset)

if (vd->vdev_nonrot) {
/* Non-rotating media. */
if (last_offset == zio_offset)
if (last_offset == zio_offset) {
MIRROR_BUMP(vdev_mirror_stat_non_rotating_linear);
return (load + zfs_vdev_mirror_non_rotating_inc);
}

/*
* Apply a seek penalty even for non-rotating devices as
* sequential I/O's can be aggregated into fewer operations on
* the device, thus avoiding unnecessary per-command overhead
* and boosting performance.
*/
MIRROR_BUMP(vdev_mirror_stat_non_rotating_seek);
return (load + zfs_vdev_mirror_non_rotating_seek_inc);
}

/* Rotating media I/O's which directly follow the last I/O. */
if (last_offset == zio_offset)
if (last_offset == zio_offset) {
MIRROR_BUMP(vdev_mirror_stat_rotating_linear);
return (load + zfs_vdev_mirror_rotating_inc);
}

/*
* Apply half the seek increment to I/O's within seek offset
* of the last I/O issued to this vdev as they should incur less
* of a seek increment.
*/
offset_diff = (int64_t)(last_offset - zio_offset);
if (ABS(offset_diff) < zfs_vdev_mirror_rotating_seek_offset)
if (ABS(offset_diff) < zfs_vdev_mirror_rotating_seek_offset) {
MIRROR_BUMP(vdev_mirror_stat_rotating_offset);
return (load + (zfs_vdev_mirror_rotating_seek_inc / 2));
}

/* Apply the full seek increment to all other I/O's. */
MIRROR_BUMP(vdev_mirror_stat_rotating_seek);
return (load + zfs_vdev_mirror_rotating_seek_inc);
}

Expand Down Expand Up @@ -387,12 +454,15 @@ vdev_mirror_child_select(zio_t *zio)
mm->mm_preferred_cnt++;
}

if (mm->mm_preferred_cnt == 1)
if (mm->mm_preferred_cnt == 1) {
MIRROR_BUMP(vdev_mirror_stat_preferred_found);
return (mm->mm_preferred[0]);
}


if (mm->mm_preferred_cnt > 1)
if (mm->mm_preferred_cnt > 1) {
MIRROR_BUMP(vdev_mirror_stat_preferred_not_found);
return (vdev_mirror_preferred_child_randomize(zio));
}

/*
* Every device is either missing or has this txg in its DTL.
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