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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/zio_inject.c
+4 -4
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@@ -117,7 +117,7 @@ freq_triggered(uint32_t frequency)
*/
uint32_t maximum = (frequency <= 100) ? 100 : ZI_PERCENTAGE_MAX;
return (spa_get_random(maximum) < frequency);
return (random_in_range(maximum) < frequency);
}
/*
@@ -347,12 +347,12 @@ zio_inject_bitflip_cb(void *data, size_t len, void *private)
{
zio_t *zio __maybe_unused = private;
uint8_t *buffer = data;
uint_t byte = spa_get_random(len);
uint_t byte = random_in_range(len);
ASSERT(zio->io_type == ZIO_TYPE_READ);
/* flip a single random bit in an abd data buffer */
buffer[byte] ^= 1 << spa_get_random(8);
buffer[byte] ^= 1 << random_in_range(8);
return (1); /* stop after first flip */
}
@@ -493,7 +493,7 @@ zio_handle_ignored_writes(zio_t *zio)
}
/* Have a "problem" writing 60% of the time */
if (spa_get_random(100) < 60)
if (random_in_range(100) < 60)
zio->io_pipeline &= ~ZIO_VDEV_IO_STAGES;
break;
}