Author: alc
Date: Sat Jun 27 21:37:36 2009
New Revision: 195122
URL: http://svn.freebsd.org/changeset/base/195122
Log:
Correct a long-standing performance bug in cluster_rbuild(). Specifically,
in the case of a file system with a block size that is less than the page
size, cluster_rbuild() looks at too many of the page's valid bits.
Consequently, it may terminate prematurely, resulting in poor performance.
Reported by: bde
Reviewed by: tegge
Approved by: re (kib)
Modified:
head/sys/kern/vfs_cluster.c
Modified: head/sys/kern/vfs_cluster.c
==============================================================================
--- head/sys/kern/vfs_cluster.c Sat Jun 27 21:23:30 2009 (r195121)
+++ head/sys/kern/vfs_cluster.c Sat Jun 27 21:37:36 2009 (r195122)
@@ -310,7 +310,9 @@ cluster_rbuild(vp, filesize, lbn, blkno,
struct bufobj *bo;
struct buf *bp, *tbp;
daddr_t bn;
- int i, inc, j;
+ off_t off;
+ long tinc, tsize;
+ int i, inc, j, toff;
KASSERT(size == vp->v_mount->mnt_stat.f_iosize,
("cluster_rbuild: size %ld != filesize %jd\n",
@@ -402,15 +404,24 @@ cluster_rbuild(vp, filesize, lbn, blkno,
* take part in the cluster. If it is partially valid
* then we stop.
*/
+ off = tbp->b_offset;
+ tsize = size;
VM_OBJECT_LOCK(tbp->b_bufobj->bo_object);
- for (j = 0;j < tbp->b_npages; j++) {
+ for (j = 0; tsize > 0; j++) {
+ toff = off & PAGE_MASK;
+ tinc = tsize;
+ if (toff + tinc > PAGE_SIZE)
+ tinc = PAGE_SIZE - toff;
VM_OBJECT_LOCK_ASSERT(tbp->b_pages[j]->object,
MA_OWNED);
- if (tbp->b_pages[j]->valid)
+ if ((tbp->b_pages[j]->valid &
+ vm_page_bits(toff, tinc)) != 0)
break;
+ off += tinc;
+ tsize -= tinc;
}
VM_OBJECT_UNLOCK(tbp->b_bufobj->bo_object);
- if (j != tbp->b_npages) {
+ if (tsize > 0) {
bqrelse(tbp);
break;
}
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