On Fri, Jun 15, 2012 at 01:25:26PM +0200, Bernd Schubert wrote: > On 06/15/2012 02:16 AM, Dave Chinner wrote: > >Oh, I just noticed you are might be using CFQ (it's the default in > >dmesg). Don't - CFQ is highly unsuited for hardware RAID - it's > >hueristically tuned to work well on sngle SATA drives. Use deadline, > >or preferably for hardware RAID, noop. > > I'm not sure if noop is really a good recommendation even with hw > raid, especially if the the request queue size is high. This week I > did some benchmarks with a high rq write size (triggered with > sync_file_range(..., SYNC_FILE_RANGE_WRITE) ) and with noop > concuring reads then almost entirely got stalled. > With deadline read/write balance was much better, although writes > still had been preferred (with sync_file_range() and without). I > always thought deadline prefers reads and I hope I find some time > later on to investigate further what was going on. > Test had been on a netapp E5400 hw raid, so rather high end hw raid. Sounds like a case of the IO scheduler queue and/or CTQ being too deep. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
