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| author |   mpi <mpi@openbsd.org> | 2016-03-06 19:15:23 +0000 |
|---|---|---|
| committer | mpi <mpi@openbsd.org> | 2016-03-06 19:15:23 +0000 |
| commit | 427674adb592a841bdc31a54b9cf9b5cfa6e3cc5 (patch) | |
| tree | 60041be13aef6bdabb2185935a9a89e3d176a6db | |
| parent | Merge db_elf_sym_values() into db_symbol_values(). (diff) | |
| download | wireguard-openbsd-427674adb592a841bdc31a54b9cf9b5cfa6e3cc5.tar.xz wireguard-openbsd-427674adb592a841bdc31a54b9cf9b5cfa6e3cc5.zip | |
Do not fetch the same block multiple times if it is already present
in the buffer cache.
When the Dynamic Buffer Cache has been introduced bread_cluster()
became the replacement of cluster_read(). However this function
did not consider the B_CACHE flag of the first buffer of a cluster
like its predecessor did.
This improves a lot read operations on MSDOSFS while reducing the
number of DMA operations.
ok beck@
| -rw-r--r-- | sys/kern/vfs_bio.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c index aeb9c4121f4..774fbe03b00 100644 --- a/sys/kern/vfs_bio.c +++ b/sys/kern/vfs_bio.c @@ -1,4 +1,4 @@ -/* $OpenBSD: vfs_bio.c,v 1.171 2015/11/28 21:52:02 beck Exp $ */ +/* $OpenBSD: vfs_bio.c,v 1.172 2016/03/06 19:15:23 mpi Exp $ */ /* $NetBSD: vfs_bio.c,v 1.44 1996/06/11 11:15:36 pk Exp $ */ /* @@ -461,13 +461,19 @@ bread_cluster(struct vnode *vp, daddr_t blkno, int size, struct buf **rbpp) *rbpp = bio_doread(vp, blkno, size, 0); + /* + * If the buffer is in the cache skip any I/O operation. + */ + if (ISSET((*rbpp)->b_flags, B_CACHE)) + goto out; + if (size != round_page(size)) goto out; if (VOP_BMAP(vp, blkno + 1, NULL, &sblkno, &maxra)) goto out; - maxra++; + maxra++; if (sblkno == -1 || maxra < 2) goto out; |