On Fri, Oct 04, 2013 at 11:16:12AM -0400, Jason Baron wrote: > On 10/03/2013 05:50 PM, Andrew Morton wrote: > > On Tue, 1 Oct 2013 17:08:14 +0000 (GMT) Jason Baron <jbaron@xxxxxxxxxx> wrote: > > > >> When calling EPOLL_CTL_ADD for an epoll file descriptor that is attached > >> directly to a wakeup source, we do not need to take the global 'epmutex', > >> unless the epoll file descriptor is nested. The purpose of taking > >> the 'epmutex' on add is to prevent complex topologies such as loops and > >> deep wakeup paths from forming in parallel through multiple EPOLL_CTL_ADD > >> operations. However, for the simple case of an epoll file descriptor > >> attached directly to a wakeup source (with no nesting), we do not need > >> to hold the 'epmutex'. > >> > >> This patch along with 'epoll: optimize EPOLL_CTL_DEL using rcu' improves > >> scalability on larger systems. Quoting Nathan Zimmer's mail on SPECjbb > >> performance: > >> > >> " > >> On the 16 socket run the performance went from 35k jOPS to 125k jOPS. > >> In addition the benchmark when from scaling well on 10 sockets to scaling well > >> on just over 40 sockets. > >> > >> ... > >> > >> Currently the benchmark stops scaling at around 40-44 sockets but it seems like > >> I found a second unrelated bottleneck. > >> " > > I couldn't resist fiddling. Please review > > > > From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Subject: epoll-do-not-take-global-epmutex-for-simple-topologies-fix > > > > - use `bool' for boolean variables > > - remove unneeded/undesirable cast of void* > > - add missed ep_scan_ready_list() kerneldoc > > Hi Andrew, > > Looks good to me. Feel free to add: > > Reviewed-by: Jason Baron <jbaron@xxxxxxxxxx> > > Thanks, > > -Jason Just finished rerunning the benchmarks with this latest patchset, including the fiddling, and it still looks great. Thanks, Nate -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
