vfs: increase shrinker batch size (8ab47664) · Commits · 戴 / test

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>

Documentation/filesystems/vfs.txt

+6 −0

Original line number	Diff line number	Diff line
		@@ -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.

fs/super.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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;

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