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Reduce number of metaslab preload taskq threads.

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Before this change ZFS created threads for 50% of CPUs for each top-
level vdev.  Plus it created the same number of threads for embedded
log groups (that have only one metaslab and don't need any preload).
As result, on system with 80 CPUs and pool of 60 vdevs this resulted
in 4800 metaslab preload threads, that is absolutely insane.

This patch changes the preload threads to 50% of CPUs in one taskq
per pool, so on the mentioned system it will be only 40 threads.

Among other things this fixes zdb on the mentioned system and pool
on FreeBSD, that failed to create so many threads in one process.

Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15319
This commit is contained in:
Alexander Motin
2023-10-06 12:04:00 -04:00
committed by Brian Behlendorf
parent c27277daac
commit bcd010d3a5
6 changed files with 37 additions and 47 deletions
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module/os/freebsd/zfs/sysctl_os.c
-22
View File
@@ -596,28 +596,6 @@ SYSCTL_UINT(_vfs_zfs_metaslab, OID_AUTO, df_free_pct,
" space map to continue allocations in a first-fit fashion");
/* END CSTYLED */
/*
* Percentage of all cpus that can be used by the metaslab taskq.
*/
extern int metaslab_load_pct;
/* BEGIN CSTYLED */
SYSCTL_INT(_vfs_zfs_metaslab, OID_AUTO, load_pct,
CTLFLAG_RWTUN, &metaslab_load_pct, 0,
"Percentage of cpus that can be used by the metaslab taskq");
/* END CSTYLED */
/*
* Max number of metaslabs per group to preload.
*/
extern uint_t metaslab_preload_limit;
/* BEGIN CSTYLED */
SYSCTL_UINT(_vfs_zfs_metaslab, OID_AUTO, preload_limit,
CTLFLAG_RWTUN, &metaslab_preload_limit, 0,
"Max number of metaslabs per group to preload");
/* END CSTYLED */
/* mmp.c */
int