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Reduce the scope of the VM object locking in brelse(). In my tests, this

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change reduced the total number of VM object lock acquisitions by brelse()
by 74%.

Sponsored by:	EMC / Isilon Storage Division
This commit is contained in:
Alan Cox 2013-06-02 16:18:03 +00:00
parent e45547006e
commit 39a4cd0cec
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=251257
1 changed files with 4 additions and 2 deletions
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6
sys/kern/vfs_bio.c
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@ -1522,7 +1522,6 @@ brelse(struct buf *bp)
*/
resid = bp->b_bufsize;
foff = bp->b_offset;
VM_OBJECT_WLOCK(obj);
for (i = 0; i < bp->b_npages; i++) {
int had_bogus = 0;
@ -1536,6 +1535,7 @@ brelse(struct buf *bp)
poff = OFF_TO_IDX(bp->b_offset);
had_bogus = 1;
VM_OBJECT_RLOCK(obj);
for (j = i; j < bp->b_npages; j++) {
vm_page_t mtmp;
mtmp = bp->b_pages[j];
@ -1547,6 +1547,7 @@ brelse(struct buf *bp)
bp->b_pages[j] = mtmp;
}
}
VM_OBJECT_RUNLOCK(obj);
if ((bp->b_flags & (B_INVAL | B_UNMAPPED)) == 0) {
BUF_CHECK_MAPPED(bp);
@ -1564,14 +1565,15 @@ brelse(struct buf *bp)
(PAGE_SIZE - poffset) : resid;
KASSERT(presid >= 0, ("brelse: extra page"));
VM_OBJECT_WLOCK(obj);
vm_page_set_invalid(m, poffset, presid);
VM_OBJECT_WUNLOCK(obj);
if (had_bogus)
printf("avoided corruption bug in bogus_page/brelse code\n");
}
resid -= PAGE_SIZE - (foff & PAGE_MASK);
foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK;
}
VM_OBJECT_WUNLOCK(obj);
if (bp->b_flags & (B_INVAL | B_RELBUF))
vfs_vmio_release(bp);