Re: A unresponsive file system can hang all I/O in the system onlinux-2.6.23-rc6 (dirty_thresh problem?)

From: Andrew Morton
Date: Fri Sep 28 2007 - 15:28:03 EST

On Fri, 28 Sep 2007 15:16:11 -0400 Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote:

> On Fri, 2007-09-28 at 11:49 -0700, Andrew Morton wrote:
> > On Fri, 28 Sep 2007 13:00:53 -0400 Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote:
> > > Do these patches also cause the memory reclaimers to steer clear of
> > > devices that are congested (and stop waiting on a congested device if
> > > they see that it remains congested for a long period of time)? Most of
> > > the collateral blocking I see tends to happen in memory allocation...
> > >
> >
> > No, they don't attempt to do that, but I suspect they put in place
> > infrastructure which could be used to improve direct-reclaimer latency. In
> > the throttle_vm_writeout() path, at least.
> >
> > Do you know where the stalls are occurring? throttle_vm_writeout(), or via
> > direct calls to congestion_wait() from page_alloc.c and vmscan.c? (running
> > sysrq-w five or ten times will probably be enough to determine this)
> Looking back, they were getting caught up in
> balance_dirty_pages_ratelimited() and friends. See the attached
> example...

that one is nfs-on-loopback, which is a special case, isn't it?

NFS on loopback used to hang, but then we fixed it. It looks like we
broke it again sometime in the intervening four years or so.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at