* Tim Chen <tim.c.c...@linux.intel.com> wrote:
> For version 8 of the patchset, we included the patch from Waiman to
> streamline wakeup operations and also optimize the MCS lock used in
> rwsem and mutex.
I'd be feeling a lot easier about this patch series if you also had
performance figures that show how mmap_sem is affected.
These:
> Tim got the following improvement for exim mail server
> workload on 40 core system:
>
> Alex+Tim's patchset: +4.8%
> Alex+Tim+Waiman's patchset: +5.3%
appear to be mostly related to the anon_vma->rwsem. But once that lock is
changed to an rwlock_t, this measurement falls away.
Peter Zijlstra suggested the following testcase:
===============================>
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.
<===============================
this could be put into a standalone testcase, or you could add it as a new
subcommand of 'perf bench', which already has some pthread code, see for
example in tools/perf/bench/sched-messaging.c. Adding:
perf bench mm threads
or so would be a natural thing to have.
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
