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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/os/linux/zfs/arc_os.c
+2 -2
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@@ -437,7 +437,7 @@ arc_available_memory(void)
int64_t lowest = INT64_MAX;
/* Every 100 calls, free a small amount */
if (spa_get_random(100) == 0)
if (random_in_range(100) == 0)
lowest = -1024;
return (lowest);
@@ -458,7 +458,7 @@ arc_all_memory(void)
uint64_t
arc_free_memory(void)
{
return (spa_get_random(arc_all_memory() * 20 / 100));
return (random_in_range(arc_all_memory() * 20 / 100));
}
void