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 -- 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
