Re: [PATCH 10/10] xfs: don't cache inodes read through bulkstat

Ben Myers
2012-03-15T18:14:20Z

On Wed, Mar 07, 2012 at 03:50:28PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> When we read inodes via bulkstat, we generally only read them once
> and then throw them away - they never get used again. If we retain
> them in cache, then it simply causes the working set of inodes and
> other cached items to be reclaimed just so the inode cache can grow.
>
> Avoid this problem by marking inodes read by bulkstat as not to be
> cached and check this flag in .drop_inode to determine whether the
> inode should be added to the VFS LRU or not. If the inode lookup
> hits an already cached inode, then don't set the flag. If the inode
> lookup hits an inode marked with no cache flag, remove the flag and
> allow it to be cached once the current reference goes away.
>
> Inodes marked as not cached will get cleaned up by the background
> inode reclaim or via memory pressure, so they will still generate
> some short term cache pressure. They will, however, be reclaimed
> much sooner and in preference to cache hot inodes.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_iget.c | 8 ++++++--
> fs/xfs/xfs_inode.h | 4 +++-
> fs/xfs/xfs_itable.c | 3 ++-
> fs/xfs/xfs_super.c | 17 +++++++++++++++++
> 4 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
> index 93fc1dc..20ddb1e 100644
> --- a/fs/xfs/xfs_iget.c
> +++ b/fs/xfs/xfs_iget.c
> @@ -290,7 +290,7 @@ xfs_iget_cache_hit(
> if (lock_flags != 0)
> xfs_ilock(ip, lock_flags);
>
> - xfs_iflags_clear(ip, XFS_ISTALE);
> + xfs_iflags_clear(ip, XFS_ISTALE | XFS_IDONTCACHE);

If XFS_IGET_DONTCACHE is set, maybe you don't want to clear
XFS_IDONTCACHE.