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Optimize small random numbers generation

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In all places except two spa_get_random() is used for small values,
and the consumers do not require well seeded high quality values.
Switch those two exceptions directly to random_get_pseudo_bytes()
and optimize spa_get_random(), renaming it to random_in_range(),
since it is not related to SPA or ZFS in general.

On FreeBSD directly map random_in_range() to new prng32_bounded() KPI
added in FreeBSD 13.  On Linux and in user-space just reduce the type
used to uint32_t to avoid more expensive 64bit division.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored-By: iXsystems, Inc.
Closes #12183
This commit is contained in:
Alexander Motin
2021-06-22 19:35:23 -04:00
committed by GitHub
parent ba91311561
commit 29274c9f6d
16 changed files with 83 additions and 45 deletions
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module/zfs/spa.c
+3 -3
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@@ -3175,7 +3175,7 @@ spa_activity_check(spa_t *spa, uberblock_t *ub, nvlist_t *config)
import_delay = spa_activity_check_duration(spa, ub);
/* Add a small random factor in case of simultaneous imports (0-25%) */
import_delay += import_delay * spa_get_random(250) / 1000;
import_delay += import_delay * random_in_range(250) / 1000;
import_expire = gethrtime() + import_delay;
@@ -4619,7 +4619,7 @@ spa_ld_checkpoint_rewind(spa_t *spa)
vdev_t *svd[SPA_SYNC_MIN_VDEVS] = { NULL };
int svdcount = 0;
int children = rvd->vdev_children;
int c0 = spa_get_random(children);
int c0 = random_in_range(children);
for (int c = 0; c < children; c++) {
vdev_t *vd = rvd->vdev_child[(c0 + c) % children];
@@ -9111,7 +9111,7 @@ spa_sync_rewrite_vdev_config(spa_t *spa, dmu_tx_t *tx)
vdev_t *svd[SPA_SYNC_MIN_VDEVS] = { NULL };
int svdcount = 0;
int children = rvd->vdev_children;
int c0 = spa_get_random(children);
int c0 = random_in_range(children);
for (int c = 0; c < children; c++) {
vdev_t *vd =