Go to file
Brian Behlendorf ab26409db7 Linux 3.1 compat, super_block->s_shrink
The Linux 3.1 kernel has introduced the concept of per-filesystem
shrinkers which are directly assoicated with a super block.  Prior
to this change there was one shared global shrinker.

The zfs code relied on being able to call the global shrinker when
the arc_meta_limit was exceeded.  This would cause the VFS to drop
references on a fraction of the dentries in the dcache.  The ARC
could then safely reclaim the memory used by these entries and
honor the arc_meta_limit.  Unfortunately, when per-filesystem
shrinkers were added the old interfaces were made unavailable.

This change adds support to use the new per-filesystem shrinker
interface so we can continue to honor the arc_meta_limit.  The
major benefit of the new interface is that we can now target
only the zfs filesystem for dentry and inode pruning.  Thus we
can minimize any impact on the caching of other filesystems.

In the context of making this change several other important
issues related to managing the ARC were addressed, they include:

* The dnlc_reduce_cache() function which was called by the ARC
to drop dentries for the Posix layer was replaced with a generic
zfs_prune_t callback.  The ZPL layer now registers a callback to
drop these dentries removing a layering violation which dates
back to the Solaris code.  This callback can also be used by
other ARC consumers such as Lustre.

  arc_add_prune_callback()
  arc_remove_prune_callback()

* The arc_reduce_dnlc_percent module option has been changed to
arc_meta_prune for clarity.  The dnlc functions are specific to
Solaris's VFS and have already been largely eliminated already.
The replacement tunable now represents the number of bytes the
prune callback will request when invoked.

* Less aggressively invoke the prune callback.  We used to call
this whenever we exceeded the arc_meta_limit however that's not
strictly correct since it results in over zeleous reclaim of
dentries and inodes.  It is now only called once the arc_meta_limit
is exceeded and every effort has been made to evict other data from
the ARC cache.

* More promptly manage exceeding the arc_meta_limit.  When reading
meta data in to the cache if a buffer was unable to be recycled
notify the arc_reclaim thread to invoke the required prune.

* Added arcstat_prune kstat which is incremented when the ARC
is forced to request that a consumer prune its cache.  Remember
this will only occur when the ARC has no other choice.  If it
can evict buffers safely without invoking the prune callback
it will.

* This change is also expected to resolve the unexpect collapses
of the ARC cache.  This would occur because when exceeded just the
arc_meta_limit reclaim presure would be excerted on the arc_c
value via arc_shrink().  This effectively shrunk the entire cache
when really we just needed to reclaim meta data.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #466
Closes #292
2012-01-11 11:46:02 -08:00
cmd Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
config Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
dracut Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
etc Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
include Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
lib Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
man Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
module Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
patches Add build system 2010-08-31 13:41:27 -07:00
scripts Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
udev Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
.gitignore Ignore unsigned module build products 2010-03-09 14:14:09 -08:00
AUTHORS Add "ashift" property to zpool create 2011-06-17 16:35:49 -07:00
autogen.sh Make autogen.sh executable 2011-07-26 10:15:35 -07:00
ChangeLog Add build system 2010-08-31 13:41:27 -07:00
configure Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
configure.ac Add make rule for building Arch Linux packages 2011-12-14 19:14:23 -08:00
COPYING Relocate COPYING+COPYRIGHT, remove README cruft 2008-12-01 15:34:53 -08:00
COPYRIGHT Update COPYRIGHT to reference zpios CDDL exceptions. 2010-05-18 14:25:28 -07:00
DISCLAIMER Update COPYRIGHT and DISCLAIMER. 2010-05-18 10:32:23 -07:00
Makefile.am Add make rule for building Arch Linux packages 2011-12-14 19:14:23 -08:00
Makefile.in Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
META Prep zfs-0.6.0-rc6 tag 2011-10-06 14:10:45 -07:00
OPENSOLARIS.LICENSE Add CDDL license file 2008-12-01 14:49:34 -08:00
PKGBUILD-zfs-modules.in Add make rule for building Arch Linux packages 2011-12-14 19:14:23 -08:00
PKGBUILD-zfs.in Add make rule for building Arch Linux packages 2011-12-14 19:14:23 -08:00
README.markdown Fix markdown rendering 2010-09-15 09:09:37 -07:00
zfs_config.h.in Linux 3.1 compat, super_block->s_shrink 2012-01-11 11:46:02 -08:00
zfs-modules.spec.in Fix depmod warning 2011-11-10 10:26:06 -08:00
zfs-script-config.sh.in Unconditionally load core kernel modules 2010-11-11 11:38:25 -08:00
ZFS.RELEASE Update to onnv_147 2010-08-26 14:24:34 -07:00
zfs.spec.in Include distribution in release 2011-10-19 11:43:27 -07:00

Native ZFS for Linux! ZFS is an advanced file system and volume manager which was originally developed for Solaris. It has been successfully ported to FreeBSD and now there is a functional Linux ZFS kernel port too. The port currently includes a fully functional and stable SPA, DMU, and ZVOL with a ZFS Posix Layer (ZPL) on the way!

$ ./configure
$ make pkg

Full documentation for building, configuring, and using ZFS can be found at: http://zfsonlinux.org