Expose zfetch_max_idistance tunable

FreeBSD had this value tunable before the switch to the new OpenZFS.
The tunable name has changed, breaking legacy compat.

Restore legacy compat for this tunable, properly expose the tunable
with the new name on all platforms, and document it in
zfs-module-parameters(5).

While here, clean up the documentation for zfetch_max_distance a bit.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #11038
This commit is contained in:
Ryan Moeller 2020-10-13 12:32:34 -04:00 committed by GitHub
parent 61868bb14d
commit 7dfc56d866
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 20 additions and 5 deletions

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@ -827,9 +827,20 @@ Default value: \fB1,048,576\fR.
\fBzfetch_max_distance\fR (uint)
.ad
.RS 12n
Max bytes to prefetch per stream (default 8MB).
Max bytes to prefetch per stream.
.sp
Default value: \fB8,388,608\fR.
Default value: \fB8,388,608\fR (8MB).
.RE
.sp
.ne 2
.na
\fBzfetch_max_idistance\fR (uint)
.ad
.RS 12n
Max bytes to prefetch indirects for per stream.
.sp
Default vaule: \fB67,108,864\fR (64MB).
.RE
.sp

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@ -300,8 +300,9 @@ SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, max_distance, CTLFLAG_RWTUN,
/* max bytes to prefetch indirects for per stream (default 64MB) */
extern uint32_t zfetch_max_idistance;
SYSCTL_UINT(_vfs_zfs_prefetch, OID_AUTO, max_idistance, CTLFLAG_RWTUN,
&zfetch_max_idistance, 0, "Max bytes to prefetch indirects for per stream");
SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, max_idistance, CTLFLAG_RWTUN,
&zfetch_max_idistance, 0,
"Max bytes to prefetch indirects for per stream (LEGACY)");
/* dsl_pool.c */

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@ -457,7 +457,10 @@ ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, min_sec_reap, UINT, ZMOD_RW,
"Min time before stream reclaim");
ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_distance, UINT, ZMOD_RW,
"Max bytes to prefetch per stream (default 8MB)");
"Max bytes to prefetch per stream");
ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_idistance, UINT, ZMOD_RW,
"Max bytes to prefetch indirects for per stream");
ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, array_rd_sz, ULONG, ZMOD_RW,
"Number of bytes in a array_read");