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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/metaslab.c
+1 -1
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@@ -5070,7 +5070,7 @@ metaslab_alloc_dva(spa_t *spa, metaslab_class_t *mc, uint64_t psize,
* damage can result in extremely long reconstruction times. This
* will also test spilling from special to normal.
*/
if (psize >= metaslab_force_ganging && (spa_get_random(100) < 3)) {
if (psize >= metaslab_force_ganging && (random_in_range(100) < 3)) {
metaslab_trace_add(zal, NULL, NULL, psize, d, TRACE_FORCE_GANG,
allocator);
return (SET_ERROR(ENOSPC));