vfs: increase shrinker batch size

Now that the per-sb shrinker is responsible for shrinking 2 or more
caches, increase the batch size to keep econmies of scale for
shrinking each cache.  Increase the shrinker batch size to 1024
objects.

To allow for a large increase in batch size, add a conditional
reschedule to prune_icache_sb() so that we don't hold the LRU spin
lock for too long. This mirrors the behaviour of the
__shrink_dcache_sb(), and allows us to increase the batch size
without needing to worry about problems caused by long lock hold
times.

To ensure that filesystems using the per-sb shrinker callouts don't
cause problems, document that the object freeing method must
reschedule appropriately inside loops.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Dave Chinner 2011-07-08 14:14:45 +10:00 committed by Al Viro
parent 0e1fdafd93
commit 8ab47664d5
2 changed files with 7 additions and 0 deletions

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@ -317,6 +317,12 @@ or bottom half).
the VM is trying to reclaim under GFP_NOFS conditions, hence this
method does not need to handle that situation itself.
Implementations must include conditional reschedule calls inside any
scanning loop that is done. This allows the VFS to determine
appropriate scan batch sizes without having to worry about whether
implementations will cause holdoff problems due to large scan batch
sizes.
Whoever sets up the inode is responsible for filling in the "i_op" field. This
is a pointer to a "struct inode_operations" which describes the methods that
can be performed on individual inodes.

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@ -182,6 +182,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
s->s_shrink.seeks = DEFAULT_SEEKS;
s->s_shrink.shrink = prune_super;
s->s_shrink.batch = 1024;
}
out:
return s;