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

[Mel Gorman]

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
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