* Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>