On Thu, Sep 20, 2012 at 04:33:09AM +0000, Markus Stockhausen wrote: > > Fundamentally, you are doing it all wrong. High throughput, low > > latency NFS servers write dirty data to disk fast, not leave it > > memory until you run out of clean memory because that causes > > everything to block waiting for writeback IO completion to be ale to > > free memory... > > Maybe I did not make it clear enough. Plenty clear enough. Maybe I did not make it clear enough: Nobody has the time to try to diagnose a problem on a configuration that is obviously broken and pessimal for writeback behaviour. The first step is to report your actual problem, not an artificial behaviour you *think* demonstrates the same problem.... > The above setup is only > for demonstration purposes. To expose the problem better. In > real life we can see stalls tat thange from 0.5-1 seconds. Even > with all caches active, small dirty writeback settings and unlimited > bandwidth. So describe the application, etc that you see this problem. Start with: http://xfs.org/index.php/XFS_FAQ#Q:_What_information_should_I_include_when_reporting_a_problem.3F and we can go from there. > In between I found others complaining about the same problem: > > http://lwn.net/Articles/486313/ > http://oss.sgi.com/archives/xfs/2011-09/msg00189.html How do you know they are the same problem? Indeed, they aren't even writeback problems - they are application IO latency issues caused by the introduction of stable pages during writeback. > So just one last question: Can I savely revert the the mentioned > commit d76ee18a8551e33ad7dbd55cac38bc7b094f3abb if I only > write data to a battery backed up hardware raid controller on a > server that is attached to an UPS? NFS servers don't use mmap, so that patch is not causing your writeback problems. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
