On Fri, May 31, 2013 at 04:15:40PM +0200, jens kusch wrote: > Hi all, > > we have a problem with nfsd performance in 2.6.32. They don't seem > to able to cope with the load. This is different in 2.6.18. Anybody > seen this before? > > On Linux 2.6.32: > > - IOs are often processed by nfsd processes in a delayed fashion, as > if they have been queued before (seen from application traces). > - NFS pool statistics show only a smaller fraction processed > immediately (10..20%). The rest is queued or delayed. > - On the other hand there are lots of nfsd processes that sit idle > at the same time! > - CPU usage is very unevenly distributed among the nfsd servers, > many are never used > > I'd just like to emphasize one detail: note the output from > /proc/fs/nfsd/pool_stats below: > > # pool packets-arrived sockets-enqueued threads-woken > overloads-avoided threads-timedout > 0 7740103 1837083 885771 1837081 480 > > The stat overloads-avoided always gets incremented in our runs. Here > is a brief description: The patch that added the "overload-avoidance" thing didn't work in practice, and I couldn't figure out what it was meant to do, so it got revoked with 78c210efdefe07131f91ed512a3308b15bb14e2f Revert "knfsd: avoid overloading the CPU scheduler with enormous load averages" Does appling that revoke help? --b. > > Counts how many times the sunrpc server layer chose not to wake an > nfsd thread, despite the presence of idle nfsd threads, because too > many nfsd threads had been recently woken but could not get enough > CPU time to actually run. In our runs, CPU utilization never gets > close to 100%, so I wonder why NFS decided not to wake up one of the > idle threads we see. > > In our runs, CPU utilization never gets close to 100%, so I wonder > why NFS decided not to wake up one of the idle threads we see. > > > On Linux 2.6.18 > > - Performance via NFS is better > - CPU usage is more evenly distributed among the nfsd processes, all > nfsd processes are really used > > We would appreciate any hint about what could be wrong in 2.6.32. > > Best regards, > Jens > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
