Re: [PATCH 0/5] Reduce GFP_ATOMIC allocation failures, candidate fix V3

Mel Gorman
2009-11-16T17:57:47Z

On Fri, Nov 13, 2009 at 10:04:21AM +0100, Frans Pop wrote:
> On Thursday 12 November 2009, Mel Gorman wrote:
> > Changelog since V2
> > o Dropped the kswapd-quickly-notice-high-order patch. In more detailed
> > testing, it made latencies even worse as kswapd slept more on
> > high-order congestion causing order-0 direct reclaims.
> > o Added changes to how congestion_wait() works
> > o Added a number of new patches altering the behaviour of reclaim
>
> I have tested this series on top of .32-rc7. First impression is that it
> does seem to improve my test case, but does not yet completely solve it.
>
> My last gitk instance now loads more smoothly for most of the time it takes
> to complete, but I still see a choke point where things freeze for a while
> and where I get SKB allocation errors from my wireless.
> However, that choke point does seem to happen later and to be shorter than
> without the patches.
>

I haven't fully figured out why this makes a difference yet, but with
.32-rc7 and these patches, could you retry the test except beforehand do

cd /sys
for SYS in `find -name low_latency`; do
echo 0 > $SYS
done

I believe the low_latency logic might be interfering with the number of
clean pages available for kswapd to reclaim.

Thanks

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab