Re: Root-causing kswapd spinning on Sandy Bridge laptops?

[Mel Gorman <mgorman@suse.de>]

On Fri, Jun 24, 2011 at 02:54:11PM -0400, Chris Mason wrote:
> Excerpts from Andi Kleen's message of 2011-06-24 14:44:12 -0400:
> > Andrew Lutomirski <luto@mit.edu> writes:
> > 
> > [Putting the Intel graphics driver developers in cc.]
> > 
> > > I'm back :-/
> > >
> > > I just triggered the kswapd bug on 2.6.39.1, which has the
> > > cond_resched in shrink_slab.  This time my system's still usable (I'm
> > > tying this email on it), but kswapd0 is taking 100% cpu.  It *does*
> > > schedule (tested by setting its affinity the same as another CPU hog
> > > and confirming that each one gets 50%).
> > >
> > > It appears to be calling i915_gem_inactive_shrink in a loop.  I have
> > > probes on entry and return of i915_gem_inactive_shrink and on return
> > > of shrink_slab.  I see:
> > >
> > >          kswapd0    47 [000] 59599.956573: mm_vmscan_kswapd_wake: nid=0 order=0
> > >          kswapd0    47 [000] 59599.956575: shrink_zone:
> > > (ffffffff810c848c) priority=12 zone=ffff8801005fe000
> > >          kswapd0    47 [000] 59599.956576: shrink_zone_return:
> > > (ffffffff810c848c <- ffffffff810c96c6) arg1=0
> > >          kswapd0    47 [000] 59599.956578: i915_gem_inactive_shrink:
> 
> A similar trace came up a bunch of times in Jejb's NMI softlockup/kswapd
> consumes the machine thread.  That one was tracked down to slub high
> order allocations.
> 
> I'm sure that one is burned in on Mel's memory, but after a while the
> individual traces fell out of the thread, and I'm not sure the i915 part
> stuck out.
> 

I expect that Jejb's lockup is also fixed by "Stop kswapd consuming
100% CPU when highest zone is small". i915 didn't help but at the end
of the day, kswapd shouldn't have been shrinking slab so aggressively.

-- 
Mel Gorman
SUSE Labs

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>