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Illumos 5138 - add tunable for maximum number of blocks freed in one txg

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Reviewed by: Adam Leventhal <adam.leventhal@delphix.com>
Reviewed by: Mattew Ahrens <mahrens@delphix.com>
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Reviewed by: Richard Elling <richard.elling@gmail.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/5138
  https://github.com/illumos/illumos-gate/commit/af3465d

Porting notes:

Because support for exposing a uint64_t parameter wasn't added
until v3.17-rc1 the zfs_free_max_blocks variable has been declared
as a unsigned long.  This is already far larger than required and
it allows us to avoid additional autoconf compatibility code.

The default value has been set to 100,000 on Linux instead of
ULONG_MAX which is used on Illumos.  This was done to limit the
number of outstanding IOs in the system when snapshots are destroyed.
This helps ensure individual TXG sync times are kept reasonable and
memory isn't wasted managing a huge backlog of outstanding IOs.

Ported by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2675
Closes #2581
This commit is contained in:
Max Grossman
2014-09-07 17:06:08 +02:00
committed by Brian Behlendorf
parent acbad6ff67
commit 36283ca233
2 changed files with 19 additions and 0 deletions
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man/man5/zfs-module-parameters.5
+11
View File
@@ -620,6 +620,17 @@ Start syncing out a transaction group if there is at least this much dirty data.
Default value: \fB67,108,864\fR.
.RE
.sp
.ne 2
.na
\fBzfs_free_max_blocks\fR (ulong)
.ad
.RS 12n
Maximum number of blocks freed in a single txg.
.sp
Default value: \fB100,000\fR.
.RE
.sp
.ne 2
.na