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SubjectRe: vmalloc performance
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Hi,

On Mon, 2010-04-19 at 00:14 +0900, Minchan Kim wrote:
> On Fri, 2010-04-16 at 15:10 +0100, Steven Whitehouse wrote:
> > Hi,
> >
> > On Fri, 2010-04-16 at 01:51 +0900, Minchan Kim wrote:
> > [snip]
> > > Thanks for the explanation. It seems to be real issue.
> > >
> > > I tested to see effect with flush during rb tree search.
> > >
> > > Before I applied your patch, the time is 50300661 us.
> > > After your patch, 11569357 us.
> > > After my debug patch, 6104875 us.
> > >
> > > I tested it as changing threshold value.
> > >
> > > threshold time
> > > 1000 13892809
> > > 500 9062110
> > > 200 6714172
> > > 100 6104875
> > > 50 6758316
> > >
> > My results show:
> >
> > threshold time
> > 100000 139309948
> > 1000 13555878
> > 500 10069801
> > 200 7813667
> > 100 18523172
> > 50 18546256
> >
> > > And perf shows smp_call_function is very low percentage.
> > >
> > > In my cases, 100 is best.
> > >
> > Looks like 200 for me.
> >
> > I think you meant to use the non _minmax version of proc_dointvec too?
>
> Yes. My fault :)
>
> > Although it doesn't make any difference for this basic test.
> >
> > The original reporter also has 8 cpu cores I've discovered. In his case
> > divided by 4 cpus where as mine are divided by 2 cpus, but I think that
> > makes no real difference in this case.
> >
> > I'll try and get some further test results ready shortly. Many thanks
> > for all your efforts in tracking this down,
> >
> > Steve.
>
> I voted "free area cache".
My results with this patch are:

vmalloc took 5419238 us
vmalloc took 5432874 us
vmalloc took 5425568 us
vmalloc took 5423867 us

So thats about a third of the time it took with my original patch, so
very much going in the right direction :-)

I did get a compile warning:
CC mm/vmalloc.o
mm/vmalloc.c: In function ‘__free_vmap_area’:
mm/vmalloc.c:454: warning: unused variable ‘prev’

....harmless, but it should be fixed before the final version,
Steve.


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