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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 Tony Hutter
parent 6fe6192796
commit f3969ea78b
16 changed files with 83 additions and 45 deletions
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include/os/linux/spl/sys/random.h
+15
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@@ -36,4 +36,19 @@ random_get_bytes(uint8_t *ptr, size_t len)
extern int random_get_pseudo_bytes(uint8_t *ptr, size_t len);
static __inline__ uint32_t
random_in_range(uint32_t range)
{
uint32_t r;
ASSERT(range != 0);
if (range == 1)
return (0);
(void) random_get_pseudo_bytes((void *)&r, sizeof (r));
return (r % range);
}
#endif /* _SPL_RANDOM_H */