* Peter Zijlstra <pet...@infradead.org> wrote:
> On Tue, Oct 01, 2013 at 09:28:15AM +0200, Ingo Molnar wrote:
>
> > That I mostly agree with, except that without a serious usecase do we
> > have a guarantee that bugs in fancies queueing in rwsems gets ironed
> > out?
>
> Methinks mmap_sem is still a big enough lock to work out a locking
> primitive :-)
I mean the AIM7 usecase probably falls away - we need to find another one
that shows the inefficiencies.
> In fact, try something like this from userspace:
>
> n-threads:
>
> pthread_mutex_lock(&mutex);
> foo = mmap();
> pthread_mutex_lock(&mutex);
>
> /* work */
>
> pthread_mutex_unlock(&mutex);
> munma(foo);
> pthread_mutex_unlock(&mutex);
>
> vs
>
> n-threads:
>
> foo = mmap();
> /* work */
> munmap(foo);
>
>
> I've had reports that the former was significantly faster than the
> latter.
That looks like a legitimate pattern that ought to trigger in many apps.
Would be nice to turn this into a:
perf bench mm thread-create
testcase or so.
Thanks,
Ingo
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