Re: REGRESSION: Performance regressions from switchinganon_vma->lock to mutex

From: Ingo Molnar
Date: Fri Jun 17 2011 - 05:14:16 EST

* Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:

> > I tried to send uli a patch to just add caching. No go. I sent
> > *another* patch to at least make glibc use a sane interface (and
> > the cache if it needs to fall back on /proc/stat for some legacy
> > reason). We'll see what happens.
> FWIW a rerun with this modified LD_PRELOAD that does caching seems
> to have the same performance as the version that does
> sched_getaffinity.
> So you're right. Caching indeed helps and my assumption that the
> child would only do it once was incorrect.

You should have known that your assumption was wrong not just from a
quick look at the strace output or a quick look at the glibc sources,
but also because i pointed out the caching angle to you in the
sysconf() discussion:


and Denys Vlasenko pointed out the caching angle as well:

But you kept pushing for your new syscall for upstream integration,
ignoring all contrary evidence and ignoring all contrary feedback,
without even *once* checking where and how it would integrate into
glibc ...


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