> On 08/09/2007 12:55 PM, Andrew Morton wrote:
> > On Thu, 9 Aug 2007 11:59:43 +0200 Matthias Hensler <matthias@wspse.de> wrote:
> >
> >> On Sat, Aug 04, 2007 at 10:44:26AM +0200, Matthias Hensler wrote:
> >>> On Fri, Aug 03, 2007 at 11:34:07AM -0700, Andrew Morton wrote:
> >>> [...]
> >>> I am also willing to try the patch posted by Richard.
> >> I want to give some update here:
> >>
> >> 1. We finally hit the problem on a third system, with a total different
> >> setup and hardware. However, again high I/O load caused the problem
> >> and the affected filesystems were mounted with noatime.
> >>
> >> 2. I installed a recompiled kernel with just the two line patch from
> >> Richard Kennedy (
http://lkml.org/lkml/2007/8/2/89). That system has 5
> >> days uptime now and counting. I believe the patch fixed the problem.
> >> However, I will continue running "vmstat 1" and the endless loop of
> >> "cat /proc/meminfo", just in case I am wrong.
> >>
> >
> > Did we ever see the /proc/meminfo and /proc/vmstat output during the stall?
> >
> > If Richard's patch has indeed fixed it then this confirms that we're seeing
> > contention over the dirty-memory limits. Richard's patch isn't really the
> > right one because it allows unlimited dirty-memory windup in some situations
> > (large number of disks with small writes, or when we perform queue congestion
> > avoidance).
> >
> > As you're seeing this happening when multiple disks are being written to it is
> > possible that the per-device-dirty-threshold patches which recently went into
> > -mm (and which appear to have a bug) will fix it.
> >
> > But I worry that the stall appears to persist *forever*. That would indicate
> > that we have a dirty-memory accounting leak, or that for some reason the
> > system has decided to stop doing writeback to one or more queues (might be
> > caused by an error in a lower-level driver's queue congestion state management).
> >
> > If it is the latter, then it could be that running "sync" will clear the
> > problem. Temporarily, at least. Because sync will ignore the queue congestion
> > state.
> >
>
> This is still a problem for people, and no fix is in sight until 2.6.24.
