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- Hold the buf lock while manipulating and inspecting its fields.

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- Use gbincore() and not incore() so that we can drop the vnode interlock
   as we acquire the buflock.
 - Use GB_LOCK_NOWAIT when getting bufs for read ahead clusters so that we
   don't block on locked bufs.
 - Convert a while loop to a howmany() that will most likely be faster on
   modern processors.  There is another while loop divide that was left
   near by because it is operating on a 64bit int and is most likely faster.
 - Cleanup the cluster_read() code a little to get rid of a goto and make
   the logic clearer.

Tested on:	x86, alpha
Tested by:	Steve Kargl <sgk@troutmask.apl.washington.edu>
Reviewd by:	arch
This commit is contained in:
Jeff Roberson 2003-03-04 21:35:28 +00:00
parent 1106937d99
commit 24deed1aaa
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=111886
1 changed files with 70 additions and 56 deletions
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126
sys/kern/vfs_cluster.c
View File

@ -176,45 +176,56 @@ cluster_read(vp, filesize, lblkno, size, cred, totread, seqcount, bpp)
lblkno += i;
}
reqbp = bp = NULL;
/*
* If it isn't in the cache, then get a chunk from
* disk if sequential, otherwise just get the block.
*/
} else {
off_t firstread = bp->b_offset;
int nblks;
int ncontigafter;
KASSERT(bp->b_offset != NOOFFSET,
("cluster_read: no buffer offset"));
ncontigafter = 0;
/*
* Compute the total number of blocks that we should read
* synchronously.
*/
if (firstread + totread > filesize)
totread = filesize - firstread;
if (totread > size) {
int nblks = 0;
int ncontigafter;
while (totread > 0) {
nblks++;
totread -= size;
}
if (nblks == 1)
goto single_block_read;
if (nblks > racluster)
nblks = racluster;
nblks = howmany(totread, size);
if (nblks > racluster)
nblks = racluster;
/*
* Now compute the number of contiguous blocks.
*/
if (nblks > 1) {
error = VOP_BMAP(vp, lblkno, NULL,
&blkno, &ncontigafter, NULL);
if (error)
goto single_block_read;
if (blkno == -1)
goto single_block_read;
if (ncontigafter == 0)
goto single_block_read;
if (ncontigafter + 1 < nblks)
nblks = ncontigafter + 1;
/*
* If this failed to map just do the original block.
*/
if (error || blkno == -1)
ncontigafter = 0;
}
/*
* If we have contiguous data available do a cluster
* otherwise just read the requested block.
*/
if (ncontigafter) {
/* Account for our first block. */
ncontigafter++;
if (ncontigafter < nblks)
nblks = ncontigafter;
bp = cluster_rbuild(vp, filesize, lblkno,
blkno, size, nblks, bp);
lblkno += (bp->b_bufsize / size);
} else {
single_block_read:
/*
* if it isn't in the cache, then get a chunk from
* disk if sequential, otherwise just get the block.
*/
bp->b_flags |= B_RAM;
bp->b_iocmd = BIO_READ;
lblkno += 1;
@ -396,31 +407,11 @@ cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
break;
}
/*
* Shortcut some checks and try to avoid buffers that
* would block in the lock. The same checks have to
* be made again after we officially get the buffer.
*/
if ((tbp = incore(vp, lbn + i)) != NULL &&
(tbp->b_flags & B_INVAL) == 0) {
if (BUF_LOCK(tbp,
LK_EXCLUSIVE | LK_NOWAIT, NULL))
break;
BUF_UNLOCK(tbp);
tbp = getblk(vp, lbn + i, size, 0, 0, GB_LOCK_NOWAIT);
for (j = 0; j < tbp->b_npages; j++) {
if (tbp->b_pages[j]->valid)
break;
}
if (j != tbp->b_npages)
break;
if (tbp->b_bcount != size)
break;
}
tbp = getblk(vp, lbn + i, size, 0, 0, 0);
/* Don't wait around for locked bufs. */
if (tbp == NULL)
break;
/*
* Stop scanning if the buffer is fully valid
@ -793,9 +784,24 @@ cluster_wbuild(vp, size, start_lbn, len)
* is delayed-write but either locked or inval, it cannot
* partake in the clustered write.
*/
if (((tbp = incore(vp, start_lbn)) == NULL) ||
((tbp->b_flags & (B_LOCKED | B_INVAL | B_DELWRI)) != B_DELWRI) ||
BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT, NULL)) {
VI_LOCK(vp);
if ((tbp = gbincore(vp, start_lbn)) == NULL) {
VI_UNLOCK(vp);
++start_lbn;
--len;
splx(s);
continue;
}
if (BUF_LOCK(tbp,
LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK, VI_MTX(vp))) {
++start_lbn;
--len;
splx(s);
continue;
}
if ((tbp->b_flags & (B_LOCKED | B_INVAL | B_DELWRI)) !=
B_DELWRI) {
BUF_UNLOCK(tbp);
++start_lbn;
--len;
splx(s);
@ -867,7 +873,9 @@ cluster_wbuild(vp, size, start_lbn, len)
* If the adjacent data is not even in core it
* can't need to be written.
*/
if ((tbp = incore(vp, start_lbn)) == NULL) {
VI_LOCK(vp);
if ((tbp = gbincore(vp, start_lbn)) == NULL) {
VI_UNLOCK(vp);
splx(s);
break;
}
@ -879,14 +887,20 @@ cluster_wbuild(vp, size, start_lbn, len)
* I/O or be in a weird state), then don't
* cluster with it.
*/
if (BUF_LOCK(tbp,
LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
VI_MTX(vp))) {
splx(s);
break;
}
if ((tbp->b_flags & (B_VMIO | B_CLUSTEROK |
B_INVAL | B_DELWRI | B_NEEDCOMMIT))
!= (B_DELWRI | B_CLUSTEROK |
!= (B_DELWRI | B_CLUSTEROK |
(bp->b_flags & (B_VMIO | B_NEEDCOMMIT))) ||
(tbp->b_flags & B_LOCKED) ||
tbp->b_wcred != bp->b_wcred ||
BUF_LOCK(tbp, LK_EXCLUSIVE | LK_NOWAIT,
NULL)) {
tbp->b_wcred != bp->b_wcred) {
BUF_UNLOCK(bp);
splx(s);
break;
}