Re: [PATCH 04/26] xfs: Improve metadata buffer reclaim accountability

Brian Foster
2019-10-11T12:39:43Z

On Wed, Oct 09, 2019 at 02:21:02PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> The buffer cache shrinker frees more than just the xfs_buf slab
> objects - it also frees the pages attached to the buffers. Make sure
> the memory reclaim code accounts for this memory being freed
> correctly, similar to how the inode shrinker accounts for pages
> freed from the page cache due to mapping invalidation.
>
> We also need to make sure that the mm subsystem knows these are
> reclaimable objects. We provide the memory reclaim subsystem with a
> a shrinker to reclaim xfs_bufs, so we should really mark the slab
> that way.
>
> We also have a lot of xfs_bufs in a busy system, spread them around
> like we do inodes.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---

Seems reasonable, but for inodes we also spread the ili zone. Should we
not be consistent with bli's as well?

Brian

> fs/xfs/xfs_buf.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index e484f6bead53..45b470f55ad7 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -324,6 +324,9 @@ xfs_buf_free(
>
> __free_page(page);
> }
> + if (current->reclaim_state)
> + current->reclaim_state->reclaimed_slab +=
> + bp->b_page_count;
> } else if (bp->b_flags & _XBF_KMEM)
> kmem_free(bp->b_addr);
> _xfs_buf_free_pages(bp);
> @@ -2064,7 +2067,8 @@ int __init
> xfs_buf_init(void)
> {
> xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
> - KM_ZONE_HWALIGN, NULL);
> + KM_ZONE_HWALIGN | KM_ZONE_SPREAD | KM_ZONE_RECLAIM,
> + NULL);
> if (!xfs_buf_zone)
> goto out;
>
> --
> 2.23.0.rc1
>