Re: [Bug #14141] order 2 page allocation failures in iwlagn

Frans Pop
2009-11-06T09:51:38Z

On Thursday 05 November 2009, Frans Pop wrote:
> On Monday 26 October 2009, Frans Pop wrote:
> > On Tuesday 20 October 2009, Mel Gorman wrote:
> > > I've attached a patch below that should allow us to cheat. When it's
> > > applied, it outputs who called congestion_wait(), how long the
> > > timeout was and how long it waited for. By comparing before and
> > > after sleep times, we should be able to see which of the callers has
> > > significantly changed and if it's something easily addressable.
> >
> > The results from this look fairly interesting (although I may be a bad
> > judge as I don't really know what I'm looking at ;-).
> >
> > I've tested with two kernels:
> > 1) 2.6.31.1: 1 test run
> > 2) 2.6.31.1 + congestion_wait() reverts: 2 test runs
>
> I've taken another look at the data from this debug patch, resulting in
> these graphs: http://people.debian.org/~fjp/tmp/kernel/congestion.pdf
>
> I think the graph may show the reason for the congestion_wait()
> regression. Horizontal axis shows time, vertical axis shows number of
> logged congestion_wait calls per type.

I'm sorry. My initial version had a skewed time axis (showed occurrences
instead of actual time). I've now uploaded a corrected version:
http://people.debian.org/~fjp/tmp/kernel/congestion.pdf

I've also uploaded a second version that shows cumulative delay per type,
which probably gives a better insight:
http://people.debian.org/~fjp/tmp/kernel/congestion2.pdf

For both the top chart is without the revert, the bottom one after the
revert.