On Thu, Jun 30, 2011 at 10:15:25AM +1000, Dave Chinner wrote: > On Wed, Jun 29, 2011 at 10:01:11AM -0400, Christoph Hellwig wrote: > > wbc->nonblocking is never set, so this whole code has been unreachable > > for a long time. I'm also not sure it would make a lot of sense - > > we'd rather finish our writeout after a short wait for the ilock > > instead of cancelling the whole ioend. > > The problem that the non-blocking code is trying to solve is only > obvious when the disk subsystem is fast enough to drive the flusher > thread to being CPU bound. > > e.g. when you have a disk subsystem doing background writeback > 10GB/s and the flusher thread is put to sleep for 50ms while we wait > for the lock, it can now only push 9.5GB/s. If we just move on, then > we'll spend that 50ms doing useful work on another dirty inode > rather than sleeping onthis one and hence maintaining a 10GB/s > background write rate. > > I'd suggest that the only thing that should be dropped is the > wbc->nonblocking check. Numbers would be good to validate that this > is still relevant, but I don't have a storage subsystem with enough > bandwidth to drive a flusher thread to being CPU bound... I just confirmed that I don't have a fast enough storage system to test this - the flusher thread uses only ~15% of a CPU @ 800MB/s writeback, so I'd need somewhere above 5GB/s of throughput to see any sort of artifact from this change.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
