Re: Processes stuck on D state on Dual Opteron

[Nick Piggin <nickpiggin@yahoo.com.au>]

Claudio Martins wrote:
> On Tuesday 05 April 2005 03:12, Andrew Morton wrote:
>
> > Claudio Martins <ctpm@rnl.ist.utl.pt> wrote:
> >
> > >   While stress testing 2.6.12-rc2 on an HP DL145 I get processes stuck
> > > in D state after some time.
> > >   This machine is a dual Opteron 248 with 2GB (ECC) on one node (the
> > > other node has no RAM modules plugged in, since this board works only
> > > with pairs).
> > >
> > >   I was using stress (http://weather.ou.edu/~apw/projects/stress/) with
> > > the following command line:
> > >
> > > stress -v -c 20 -i 12 -m 10 -d 20

[snip]

> ------------------------------------
>
>
>   Unfortunately the system Oopsed in the middle of dumping the tasks, but from 
> what I can see I'm tempted to think that this might be related to the MD 
> code. md2_raid1 is blocked on D state and, although not shown on the dump, I 
> know from ps command that md0_raid1 (the swap partition) was also on D state 
> (along with the stress processes which are responsible for hogging memory, 
> and top and df). There were about 200MB swapped out, but the swap partition 
> size is 1GB.

Looks like you may possibly have a memory allocation deadlock
(although I can't explain the NMI oops).

I would be interested to see if the following patch is of any
help to you.

Thanks,
Nick

--
SUSE Labs, Novell Inc.



Index: linux-2.6/mm/mempool.c
===================================================================
--- linux-2.6.orig/mm/mempool.c	2005-03-30 10:39:51.000000000 +1000
+++ linux-2.6/mm/mempool.c	2005-03-30 10:41:29.000000000 +1000
@@ -198,7 +198,10 @@ void * mempool_alloc(mempool_t *pool, in
 	void *element;
 	unsigned long flags;
 	DEFINE_WAIT(wait);
-	int gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
+	int gfp_nowait;
+	
+	gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */
+	gfp_nowait = gfp_mask & ~(__GFP_WAIT | __GFP_IO);
 
 	might_sleep_if(gfp_mask & __GFP_WAIT);
 repeat_alloc: