Thanks, I'll test this later on today.
On Dec 19, 2007, at 1:11 PM, Kostik Belousov wrote:
On Wed, Dec 19, 2007 at 09:13:31AM -0800, David G Lawrence wrote:
Try it with "find / -type f >/dev/null" to duplicate the problem
almost
instantly.
I was able to verify last night that (cd /; tar -cpf -) > all.tar
would
trigger the problem. I'm working getting a test running with
David's ffs_sync() workaround now, adding a few counters there
should
get this narrowed down a little more.
Unfortunately, the version of the patch that I sent out isn't
going to
help your problem. It needs to yield at the top of the loop, but
vp isn't
necessarily valid after the wakeup from the msleep. That's a
problem that
I'm having trouble figuring out a solution to - the solutions that
come
to mind will all significantly increase the overhead of the loop.
As a very inadequate work-around, you might consider lowering
kern.maxvnodes to something like 20000 - that might be low enough to
not trigger the problem, but also be high enough to not significantly
affect system I/O performance.
I think the following may be safe. It counts only the clean scanned
vnodes
and does not evaluate the vp, that indeed may be reclaimed, after
the sleep.
I never booted with the change.
diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index cbccc62..e686b97 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -1176,6 +1176,7 @@ ffs_sync(mp, waitfor, td)
struct ufsmount *ump = VFSTOUFS(mp);
struct fs *fs;
int error, count, wait, lockreq, allerror = 0;
+ int yield_count;
int suspend;
int suspended;
int secondary_writes;
@@ -1216,6 +1217,7 @@ loop:
softdep_get_depcounts(mp, &softdep_deps, &softdep_accdeps);
MNT_ILOCK(mp);
+ yield_count = 0;
MNT_VNODE_FOREACH(vp, mp, mvp) {
/*
* Depend on the mntvnode_slock to keep things stable enough
@@ -1233,6 +1235,11 @@ loop:
(IN_ACCESS | IN_CHANGE | IN_MODIFIED | IN_UPDATE)) == 0 &&
vp->v_bufobj.bo_dirty.bv_cnt == 0)) {
VI_UNLOCK(vp);
+ if (yield_count++ == 500) {
+ yield_count = 0;
+ msleep(&yield_count, MNT_MTX(mp), PZERO,
+ "ffspause", 1);
+ }
continue;
}
MNT_IUNLOCK(mp);
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