Date: Thu, 29 May 1997 16:25:07 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: Bruce Evans <bde@zeta.org.au> Cc: current@freebsd.org Subject: Re: disk cache challenged by small block sizes Message-ID: <Pine.BSF.3.95q.970529162337.390A-100000@herring.nlsystems.com> In-Reply-To: <199705291228.WAA11504@godzilla.zeta.org.au>
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On Thu, 29 May 1997, Bruce Evans wrote:
> Iozone on an ext2fs file system with the default block size of 1K on an
> (ncr) SCSI Zip disk gave the following poor results:
>
> [snip]
>
> This is probably related to slow reads from cd9660. (For cd9660, reads
> apparently aren't cached, no matter what the block size is, and reads
> with a block size of 512 are apparently repeated 4 times for each 2K
> fs block. For ext2fs, the above shows that writes are sometimes cached
> but another test shows that rereading flushes the cache.)
This is caused by my recent changes to vfs_bio to make NFS mmap work
properly. I didn't test on a filesystem with small block sizes. This
patch should fix it:
Index: vfs_bio.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/vfs_bio.c,v
retrieving revision 1.116
diff -u -r1.116 vfs_bio.c
--- vfs_bio.c 1997/05/19 14:36:36 1.116
+++ vfs_bio.c 1997/05/29 15:22:39
@@ -80,7 +80,8 @@
static void vfs_buf_set_valid(struct buf *bp, vm_ooffset_t foff,
vm_offset_t off, vm_offset_t size,
vm_page_t m);
-static void vfs_page_set_valid(struct buf *bp, vm_offset_t off, vm_page_t m);
+static void vfs_page_set_valid(struct buf *bp, vm_ooffset_t off,
+ int pageno, vm_page_t m);
static void vfs_clean_pages(struct buf * bp);
static void vfs_setdirty(struct buf *bp);
static void vfs_vmio_release(struct buf *bp);
@@ -1572,7 +1573,7 @@
}
if (bp->b_flags & B_VMIO) {
int i, resid;
- vm_ooffset_t foff, bfoff;
+ vm_ooffset_t foff;
vm_page_t m;
vm_object_t obj;
int iosize;
@@ -1582,7 +1583,6 @@
foff = (vm_ooffset_t) DEV_BSIZE * bp->b_lblkno;
else
foff = (vm_ooffset_t) vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
- bfoff = foff;
obj = vp->v_object;
if (!obj) {
panic("biodone: no object");
@@ -1624,7 +1624,7 @@
* here in the read case.
*/
if ((bp->b_flags & B_READ) && !bogusflag && resid > 0) {
- vfs_page_set_valid(bp, foff - bfoff, m);
+ vfs_page_set_valid(bp, foff, i, m);
}
/*
@@ -1818,21 +1818,25 @@
/*
* Set the valid bits in a page, taking care of the b_validoff,
* b_validend fields which NFS uses to optimise small reads. Off is
- * the offset of the page within the buf.
+ * the offset within the file and pageno is the page index within the buf.
*/
static void
-vfs_page_set_valid(struct buf *bp, vm_offset_t off, vm_page_t m)
+vfs_page_set_valid(struct buf *bp, vm_ooffset_t off, int pageno, vm_page_t m)
{
struct vnode *vp = bp->b_vp;
vm_offset_t soff, eoff;
soff = off;
- eoff = min(off + PAGE_SIZE, bp->b_bufsize);
+ eoff = off + min(PAGE_SIZE, bp->b_bufsize);
+ vm_page_set_invalid(m, soff, eoff);
if (vp->v_tag == VT_NFS) {
- soff = max((bp->b_validoff + DEV_BSIZE - 1) & -DEV_BSIZE, soff);
- eoff = min(bp->b_validend & -DEV_BSIZE, eoff);
+ vm_offset_t sv, ev;
+ sv = off + (bp->b_validoff + DEV_BSIZE - 1) & -DEV_BSIZE
+ - pageno * PAGE_SIZE;
+ ev = off + bp->b_validend & -DEV_BSIZE - pageno * PAGE_SIZE;
+ soff = max(sv, soff);
+ eoff = min(ev, eoff);
}
- vm_page_set_invalid(m, 0, PAGE_SIZE);
if (eoff > soff)
vm_page_set_validclean(m, soff, eoff - soff);
}
@@ -1851,11 +1855,16 @@
int i;
if (bp->b_flags & B_VMIO) {
- vm_object_t obj = bp->b_vp->v_object;
- vm_offset_t off;
+ struct vnode *vp = bp->b_vp;
+ vm_object_t obj = vp->v_object;
+ vm_ooffset_t foff;
+ if (vp->v_type == VBLK)
+ foff = (vm_ooffset_t) DEV_BSIZE * bp->b_lblkno;
+ else
+ foff = (vm_ooffset_t) vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
vfs_setdirty(bp);
- for (i = 0, off = 0; i < bp->b_npages; i++, off += PAGE_SIZE) {
+ for (i = 0; i < bp->b_npages; i++, foff += PAGE_SIZE) {
vm_page_t m = bp->b_pages[i];
if ((bp->b_flags & B_CLUSTER) == 0) {
@@ -1864,7 +1873,7 @@
}
vm_page_protect(m, VM_PROT_NONE);
if (clear_modify)
- vfs_page_set_valid(bp, off, m);
+ vfs_page_set_valid(bp, foff, i, m);
else if (bp->b_bcount >= PAGE_SIZE) {
if (m->valid && (bp->b_flags & B_CACHE) == 0) {
bp->b_pages[i] = bogus_page;
@@ -1886,12 +1895,18 @@
int i;
if (bp->b_flags & B_VMIO) {
- vm_offset_t off;
+ struct vnode *vp = bp->b_vp;
+ vm_object_t obj = vp->v_object;
+ vm_ooffset_t foff;
- for (i = 0, off = 0; i < bp->b_npages; i++, off += PAGE_SIZE) {
+ if (vp->v_type == VBLK)
+ foff = (vm_ooffset_t) DEV_BSIZE * bp->b_lblkno;
+ else
+ foff = (vm_ooffset_t) vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
+ for (i = 0; i < bp->b_npages; i++, foff += PAGE_SIZE) {
vm_page_t m = bp->b_pages[i];
- vfs_page_set_valid(bp, off, m);
+ vfs_page_set_valid(bp, foff, i, m);
}
}
}
--
Doug Rabson Mail: dfr@nlsystems.com
Nonlinear Systems Ltd. Phone: +44 181 951 1891
Fax: +44 181 381 1039
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