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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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