On Wed, 2011-06-15 at 23:37 +0200, Peter Zijlstra wrote:

On Wed, 2011-06-15 at 14:12 -0700, Tim Chen wrote:

quoted

Thanks to Andi for providing the info.  We've used this workaround in
our testing so it will not mask true kernel scaling bottlenecks.

http://programming.kicks-ass.net/sekrit/39-2.txt.bz2
http://programming.kicks-ass.net/sekrit/tip-2.txt.bz2

tip+sirq+linus is still slightly faster than .39 here, although removing
that sysconf() wreckage closed the gap considerably (needing to know the
number of cpus to optimize locking sounds like a trainwreck all of its
own, needing it _that_ often instead of just once at startup is even
worse).

Peter,

Fengguang's readahead fixes for tmpfs removed another bottleneck before
anon_vma->lock become dominant. https://lkml.org/lkml/2011/4/26/143)
We've found this issue when we were testing exim earlier.
It was merged in 3.0-rc2 but not in plain 2.6.39.  So with this patch on
2.6.39 we should get better comparison with 3.0-rc2.

Thanks.

Tim  


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