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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_misc.c
+9 -21
View File
@@ -1494,32 +1494,21 @@ spa_strfree(char *s)
kmem_free(s, strlen(s) + 1);
}
uint64_t
spa_get_random(uint64_t range)
{
uint64_t r;
ASSERT(range != 0);
if (range == 1)
return (0);
(void) random_get_pseudo_bytes((void *)&r, sizeof (uint64_t));
return (r % range);
}
uint64_t
spa_generate_guid(spa_t *spa)
{
uint64_t guid = spa_get_random(-1ULL);
uint64_t guid;
if (spa != NULL) {
while (guid == 0 || spa_guid_exists(spa_guid(spa), guid))
guid = spa_get_random(-1ULL);
do {
(void) random_get_pseudo_bytes((void *)&guid,
sizeof (guid));
} while (guid == 0 || spa_guid_exists(spa_guid(spa), guid));
} else {
while (guid == 0 || spa_guid_exists(guid, 0))
guid = spa_get_random(-1ULL);
do {
(void) random_get_pseudo_bytes((void *)&guid,
sizeof (guid));
} while (guid == 0 || spa_guid_exists(guid, 0));
}
return (guid);
@@ -2888,7 +2877,6 @@ EXPORT_SYMBOL(spa_maxdnodesize);
EXPORT_SYMBOL(spa_guid_exists);
EXPORT_SYMBOL(spa_strdup);
EXPORT_SYMBOL(spa_strfree);
EXPORT_SYMBOL(spa_get_random);
EXPORT_SYMBOL(spa_generate_guid);
EXPORT_SYMBOL(snprintf_blkptr);
EXPORT_SYMBOL(spa_freeze);