OpenZFS 8558, 8602 - lwp_create() returns EAGAIN

8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems

On a system with more than 80K ZFS filesystems, we've seen cases
where lwp_create() will start to fail by returning EAGAIN. The
problem being, for each of those 80K ZFS filesystems, a taskq will
be created for each dataset as part of the ZIL for each dataset.

Porting Notes:
- The new nomem taskq kstat was dropped.
- Added module options and documentation for new tunings
  zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc,
  zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct.

Reviewed by: George Wilson <[email protected]>
Reviewed by: Sebastien Roy <[email protected]>
Approved by: Robert Mustacchi <[email protected]>
Authored by: Prakash Surya <[email protected]>
Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Chris Dunlop <[email protected]>
Ported-by: Brian Behlendorf <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/8558
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772

8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure

Reviewed by: Serapheim Dimitropoulos <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>
Approved by: Robert Mustacchi <[email protected]>
Authored by: Prakash Surya <[email protected]>
Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Chris Dunlop <[email protected]>
Ported-by: Brian Behlendorf <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/8602
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545
Closes #6779 

1 files changed, 48 insertions, 0 deletions

diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
index 19ecde4f4..d94d6b395 100644
--- a/man/man5/zfs-module-parameters.5
+++ b/man/man5/zfs-module-parameters.5
@@ -1748,6 +1748,18 @@ Default value: \fB2\fR.
 .sp
 .ne 2
 .na
+\fBzfs_sync_taskq_batch_pct\fR (int)
+.ad
+.RS 12n
+This controls the number of threads used by the dp_sync_taskq.  The default
+value of 75% will create a maximum of one thread per cpu.
+.sp
+Default value: \fB75\fR.
+.RE
+
+.sp
+.ne 2
+.na
 \fBzfs_top_maxinflight\fR (int)
 .ad
 .RS 12n
@@ -2002,6 +2014,42 @@ Default value: \fB0\fR.
 .sp
 .ne 2
 .na
+\fBzfs_zil_clean_taskq_maxalloc\fR (int)
+.ad
+.RS 12n
+The maximum number of taskq entries that are allowed to be cached.  When this
+limit is exceeded itx's will be cleaned synchronously.
+.sp
+Default value: \fB1048576\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_zil_clean_taskq_minalloc\fR (int)
+.ad
+.RS 12n
+The number of taskq entries that are pre-populated when the taskq is first
+created and are immediately available for use.
+.sp
+Default value: \fB1024\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBzfs_zil_clean_taskq_nthr_pct\fR (int)
+.ad
+.RS 12n
+This controls the number of threads used by the dp_zil_clean_taskq.  The default
+value of 100% will create a maximum of one thread per cpu.
+.sp
+Default value: \fB100\fR.
+.RE
+
+.sp
+.ne 2
+.na
 \fBzil_replay_disable\fR (int)
 .ad
 .RS 12n