mirror_zfs/module
Matthew Ahrens bee5738f77 make zil max block size tunable
We've observed that on some highly fragmented pools, most metaslab
allocations are small (~2-8KB), but there are some large, 128K
allocations.  The large allocations are for ZIL blocks.  If there is a
lot of fragmentation, the large allocations can be hard to satisfy.

The most common impact of this is that we need to check (and thus load)
lots of metaslabs from the ZIL allocation code path, causing sync writes
to wait for metaslabs to load, which can take a second or more.  In the
worst case, we may not be able to satisfy the allocation, in which case
the ZIL will resort to txg_wait_synced() to ensure the change is on
disk.

To provide a workaround for this, this change adds a tunable that can
reduce the size of ZIL blocks.

External-issue: DLPX-61719
Reviewed-by: George Wilson <george.wilson@delphix.com>
Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #8865
2020-01-22 13:48:56 -08:00
..
avl Update build system and packaging 2018-05-29 16:00:33 -07:00
icp Minor style cleanup 2019-09-25 11:27:49 -07:00
lua Linux 5.3: Fix switch() fall though compiler errors 2019-09-25 11:27:50 -07:00
nvpair Use NV_ENCODE_NATIVE for nvlist encoding variable 2019-04-26 11:24:31 -07:00
spl Retire unused spl_{mutex,rwlock}_{init_fini} 2019-09-25 11:27:49 -07:00
unicode Update build system and packaging 2018-05-29 16:00:33 -07:00
zcommon Minor style cleanup 2019-09-25 11:27:49 -07:00
zfs make zil max block size tunable 2020-01-22 13:48:56 -08:00
.gitignore Prepare SPL repo to merge with ZFS repo 2018-05-29 14:51:39 -07:00
Makefile.in Linux 5.3 compat: Makefile subdir-m no longer supported 2019-09-25 11:27:50 -07:00