Re: [PATCH 4/8] xfs: Improve metadata buffer reclaim accountability

Allison Collins
2020-03-25T04:42:57Z

On 3/24/20 6:42 PM, 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>
Ok, makes sense
Reviewed-by: Allison Collins <allison.henderson@oracle.com>

> ---
> fs/xfs/xfs_buf.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index f880141a22681..9ec3eaf1c618f 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -327,6 +327,9 @@ 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);
> @@ -2114,9 +2117,11 @@ xfs_buf_delwri_pushbuf(
> int __init
> xfs_buf_init(void)
> {
> - xfs_buf_zone = kmem_cache_create("xfs_buf",
> - sizeof(struct xfs_buf), 0,
> - SLAB_HWCACHE_ALIGN, NULL);
> + xfs_buf_zone = kmem_cache_create("xfs_buf", sizeof(struct xfs_buf), 0,
> + SLAB_HWCACHE_ALIGN |
> + SLAB_RECLAIM_ACCOUNT |
> + SLAB_MEM_SPREAD,
> + NULL);
> if (!xfs_buf_zone)
> goto out;
>
>