From 14b064ceaa6f51a7426cc45b4b43685b94380658 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Thu, 27 Jan 2011 12:16:28 +1100 Subject: xfs: limit extent length for allocation to AG size Delayed allocation extents can be larger than AGs, so when trying to convert a large range we may scan every AG inside xfs_bmap_alloc_nullfb() trying to find an AG with a size larger than an AG. We should stop when we find the first AG with a maximum possible allocation size. This causes excessive CPU usage when there are lots of AGs. The same problem occurs when doing preallocation of a range larger than an AG. Fix the problem by limiting real allocation lengths to the maximum that an AG can support. This means if we have empty AGs, we'll stop the search at the first of them. If there are no empty AGs, we'll still scan them all, but that is a different problem.... Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Reviewed-by: Alex Elder --- fs/xfs/xfs_bmap.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'fs/xfs/xfs_bmap.c') diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c index 4111cd3966c..f3a3768189b 100644 --- a/fs/xfs/xfs_bmap.c +++ b/fs/xfs/xfs_bmap.c @@ -2430,7 +2430,7 @@ xfs_bmap_btalloc_nullfb( startag = ag = 0; pag = xfs_perag_get(mp, ag); - while (*blen < ap->alen) { + while (*blen < args->maxlen) { if (!pag->pagf_init) { error = xfs_alloc_pagf_init(mp, args->tp, ag, XFS_ALLOC_FLAG_TRYLOCK); @@ -2452,7 +2452,7 @@ xfs_bmap_btalloc_nullfb( notinit = 1; if (xfs_inode_is_filestream(ap->ip)) { - if (*blen >= ap->alen) + if (*blen >= args->maxlen) break; if (ap->userdata) { @@ -2498,14 +2498,14 @@ xfs_bmap_btalloc_nullfb( * If the best seen length is less than the request * length, use the best as the minimum. */ - else if (*blen < ap->alen) + else if (*blen < args->maxlen) args->minlen = *blen; /* - * Otherwise we've seen an extent as big as alen, + * Otherwise we've seen an extent as big as maxlen, * use that as the minimum. */ else - args->minlen = ap->alen; + args->minlen = args->maxlen; /* * set the failure fallback case to look in the selected @@ -2573,7 +2573,9 @@ xfs_bmap_btalloc( args.tp = ap->tp; args.mp = mp; args.fsbno = ap->rval; - args.maxlen = MIN(ap->alen, mp->m_sb.sb_agblocks); + + /* Trim the allocation back to the maximum an AG can fit. */ + args.maxlen = MIN(ap->alen, XFS_ALLOC_AG_MAX_USABLE(mp)); args.firstblock = ap->firstblock; blen = 0; if (nullfb) { @@ -2621,7 +2623,7 @@ xfs_bmap_btalloc( /* * Adjust for alignment */ - if (blen > args.alignment && blen <= ap->alen) + if (blen > args.alignment && blen <= args.maxlen) args.minlen = blen - args.alignment; args.minalignslop = 0; } else { @@ -2640,7 +2642,7 @@ xfs_bmap_btalloc( * of minlen+alignment+slop doesn't go up * between the calls. */ - if (blen > mp->m_dalign && blen <= ap->alen) + if (blen > mp->m_dalign && blen <= args.maxlen) nextminlen = blen - mp->m_dalign; else nextminlen = args.minlen; -- cgit v1.2.3-70-g09d2