diff options
| author | Paul Dagnelie <[email protected]> | 2019-08-16 08:08:21 -0700 |
|---|---|---|
| committer | Brian Behlendorf <[email protected]> | 2019-08-16 09:08:21 -0600 |
| commit | f09fda5071813751ba3fa77c28e588689795e17e (patch) | |
| tree | 164564e5c5a88412d05477214c06cda69f929858 /man/man5 | |
| parent | 9323aad14d2f99d6fff1e50cce25fa6361495ec4 (diff) | |
Cap metaslab memory usage
On systems with large amounts of storage and high fragmentation, a huge
amount of space can be used by storing metaslab range trees. Since
metaslabs are only unloaded during a txg sync, and only if they have
been inactive for 8 txgs, it is possible to get into a state where all
of the system's memory is consumed by range trees and metaslabs, and
txgs cannot sync. While ZFS knows how to evict ARC data when needed,
it has no such mechanism for range tree data. This can result in boot
hangs for some system configurations.
First, we add the ability to unload metaslabs outside of syncing
context. Second, we store a multilist of all loaded metaslabs, sorted
by their selection txg, so we can quickly identify the oldest
metaslabs. We use a multilist to reduce lock contention during heavy
write workloads. Finally, we add logic that will unload a metaslab
when we're loading a new metaslab, if we're using more than a certain
fraction of the available memory on range trees.
Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: George Wilson <[email protected]>
Reviewed-by: Sebastien Roy <[email protected]>
Reviewed-by: Serapheim Dimitropoulos <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Paul Dagnelie <[email protected]>
Closes #9128
Diffstat (limited to 'man/man5')
| -rw-r--r-- | man/man5/zfs-module-parameters.5 | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5 index c25f2f046..8a1048bee 100644 --- a/man/man5/zfs-module-parameters.5 +++ b/man/man5/zfs-module-parameters.5 @@ -389,6 +389,21 @@ Default value: \fB3600 seconds\fR (one hour) .sp .ne 2 .na +\fBzfs_metaslab_mem_limit\fR (int) +.ad +.RS 12n +When we are loading a new metaslab, we check the amount of memory being used +to store metaslab range trees. If it is over a threshold, we attempt to unload +the least recently used metaslab to prevent the system from clogging all of +its memory with range trees. This tunable sets the percentage of total system +memory that is the threshold. +.sp +Default value: \fB75 percent\fR +.RE + +.sp +.ne 2 +.na \fBzfs_vdev_default_ms_count\fR (int) .ad .RS 12n |