Date: Sat, 27 Jun 2009 21:37:36 +0000 (UTC) From: Alan Cox <alc@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r195122 - head/sys/kern Message-ID: <200906272137.n5RLbaEJ089043@svn.freebsd.org>
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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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