7.0BETA4 desktop system also periodically freezes

[Kostik Belousov]

On Wed, Jan 09, 2008 at 11:58:19PM -0500, J.R. Oldroyd wrote:
> On Wed, 09 Jan 2008 20:38:29 +0100, Kris Kennaway <kris at freebsd.org> wrote:
> >
> > 
> > OK, same requests as to the others then.
> > 
> 
> I presume you mean hwpmc...
> 
> In setting that up, I may have stumbled upon a possible cause.
> I ran pmcstat for a while and ended up with a very large output
> file.  Having not noticed any freezes during that time, I decided
> to start over with the output to a different filesystem with more
> free space.  When I removed that first output file, the resulting
> disk i/o for the block deallocation caused a very similar freeze
> for a few seconds.  And when it came back, the load average graph
> peaked up, just as before.
> 
> This appears to be repeatable:
> 
> 1. create a very large file, say 1Gb or so
> 2. remove it
> 3. observe freeze during file dealloc i/o activity
> 
> This on an ata drive, ufs filesystem with softupdates.
> 
> Folk complaining of jerky mouse syndrome (e.g., during compilations)
> may be seeing the same - the compiler creates and removes lots of
> files.
> 
> I'm not sure how this would explain those longer freezes (30s or
> several minutes) though.

For the SU-imposed jerkiness, try the patch below. Progress on developing
the change stalled somehow, and I would like to process with it.

diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 248ce22..005f915 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -2001,6 +2001,12 @@ __mnt_vnode_next(struct vnode **mvp, struct mount *mp)
 	mtx_assert(MNT_MTX(mp), MA_OWNED);
 
 	KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
+	if ((*mvp)->v_yield++ == 500) {
+		MNT_IUNLOCK(mp);
+		(*mvp)->v_yield = 0;
+		uio_yield();
+		MNT_ILOCK(mp);
+	}
 	vp = TAILQ_NEXT(*mvp, v_nmntvnodes);
 	while (vp != NULL && vp->v_type == VMARKER)
 		vp = TAILQ_NEXT(vp, v_nmntvnodes);
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index 0525a43..1ac289a 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -131,6 +131,7 @@ struct vnode {
 		struct socket	*vu_socket;	/* v unix domain net (VSOCK) */
 		struct cdev	*vu_cdev; 	/* v device (VCHR, VBLK) */
 		struct fifoinfo	*vu_fifoinfo;	/* v fifo (VFIFO) */
+		int		vu_yield;	/*   yield count (VMARKER) */
 	} v_un;
 
 	/*
@@ -185,6 +186,7 @@ struct vnode {
 #define	v_socket	v_un.vu_socket
 #define	v_rdev		v_un.vu_cdev
 #define	v_fifoinfo	v_un.vu_fifoinfo
+#define	v_yield		v_un.vu_yield
 
 /* XXX: These are temporary to avoid a source sweep at this time */
 #define v_object	v_bufobj.bo_object
diff --git a/sys/ufs/ffs/ffs_softdep.c b/sys/ufs/ffs/ffs_softdep.c
index a221b66..02cf45b 100644
--- a/sys/ufs/ffs/ffs_softdep.c
+++ b/sys/ufs/ffs/ffs_softdep.c
@@ -864,6 +864,7 @@ softdep_process_worklist(mp, full)
 		 */
 		if (loopcount++ % 128 == 0) {
 			FREE_LOCK(&lk);
+			uio_yield();
 			bwillwrite();
 			ACQUIRE_LOCK(&lk);
 		}
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