From 55a7bc5a30ff2d30d8a34fea2af9fc601b32e61a Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 4 May 2011 18:55:15 +0000 Subject: xfs: do not discard alloc btree blocks Blocks for the allocation btree are allocated from and released to the AGFL, and thus frequently reused. Even worse we do not have an easy way to avoid using an AGFL block when it is discarded due to the simple FILO list of free blocks, and thus can frequently stall on blocks that are currently undergoing a discard. Add a flag to the busy extent tracking structure to skip the discard for allocation btree blocks. In normal operation these blocks are reused frequently enough that there is no need to discard them anyway, but if they spill over to the allocation btree as part of a balance we "leak" blocks that we would otherwise discard. We could fix this by adding another flag and keeping these block in the rbtree even after they aren't busy any more so that we could discard them when they migrate out of the AGFL. Given that this would cause significant overhead I don't think it's worthwile for now. Signed-off-by: Christoph Hellwig Signed-off-by: Alex Elder --- fs/xfs/xfs_alloc.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'fs/xfs/xfs_alloc.c') diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c index 721db22c6ec9..95862bbff56b 100644 --- a/fs/xfs/xfs_alloc.c +++ b/fs/xfs/xfs_alloc.c @@ -2469,7 +2469,7 @@ xfs_free_extent( error = xfs_free_ag_extent(tp, args.agbp, args.agno, args.agbno, len, 0); if (!error) - xfs_alloc_busy_insert(tp, args.agno, args.agbno, len); + xfs_alloc_busy_insert(tp, args.agno, args.agbno, len, 0); error0: xfs_perag_put(args.pag); return error; @@ -2480,7 +2480,8 @@ xfs_alloc_busy_insert( struct xfs_trans *tp, xfs_agnumber_t agno, xfs_agblock_t bno, - xfs_extlen_t len) + xfs_extlen_t len, + unsigned int flags) { struct xfs_busy_extent *new; struct xfs_busy_extent *busyp; @@ -2504,6 +2505,7 @@ xfs_alloc_busy_insert( new->bno = bno; new->length = len; INIT_LIST_HEAD(&new->list); + new->flags = flags; /* trace before insert to be able to see failed inserts */ trace_xfs_alloc_busy(tp->t_mountp, agno, bno, len); @@ -3018,7 +3020,8 @@ xfs_alloc_busy_clear( agno = busyp->agno; } - if (do_discard && busyp->length) + if (do_discard && busyp->length && + !(busyp->flags & XFS_ALLOC_BUSY_SKIP_DISCARD)) busyp->flags = XFS_ALLOC_BUSY_DISCARDED; else xfs_alloc_busy_clear_one(mp, pag, busyp); -- cgit v1.2.1