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SubjectRe: [PATCH] slub: reduce overhead of slub_debug
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On Thu, 2011-07-07 at 21:52 +0300, Pekka Enberg wrote:
> On Thu, 7 Jul 2011, Pekka Enberg wrote:
> > > Looks good to me. Christoph, David, ?
>
> On Thu, 2011-07-07 at 13:17 -0500, Christoph Lameter wrote:
> > The reason debug code is there is because it is useless overhead typically
> > not needed. There is no point in optimizing the code that is not run in
> > production environments unless there are gross performance issues that
> > make debugging difficult. A performance patch for debugging would have to
> > cause significant performance improvements. This patch does not do that
> > nor was there such an issue to be addressed in the first place.
>
> Is there something technically wrong with the patch? Quoting the patch
> email:
>
> (Compiling some project with different options)
> make -j12 make clean
> slub_debug disabled: 1m 27s 1.2 s
> slub_debug enabled: 1m 46s 7.6 s
> slub_debug enabled + this patch: 1m 33s 3.2 s
>
> check_bytes still shows up high, but not always at the top.
>
> That's significant enough speedup for me!

We're not going to make any progress on this; Christoph conveniently
forgets the counterarguments from week to week.

--
Mathematics is the supreme nostalgia of our time.




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