Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex

Ingo Molnar
2011-06-17T09:14:13Z

* Andi Kleen <ak@linux.intel.com> 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:

http://lkml.org/lkml/2011/5/14/9

repeatedly:

http://lkml.org/lkml/2011/5/17/149

and Denys Vlasenko pointed out the caching angle as well:

http://lkml.org/lkml/2011/5/17/183

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 ...

Thanks,

Ingo