Chris Mason wrote: > On Thursday 31 January 2008, Jan Kara wrote: > > On Thu 31-01-08 11:56:01, Chris Mason wrote: > > > On Thursday 31 January 2008, Al Boldi wrote: > > > > The big difference between ordered and writeback is that once the > > > > slowdown starts, ordered goes into ~100% iowait, whereas writeback > > > > continues 100% user. > > > > > > Does data=ordered write buffers in the order they were dirtied? This > > > might explain the extreme problems in transactional workloads. > > > > Well, it does but we submit them to block layer all at once so > > elevator should sort the requests for us... > > nr_requests is fairly small, so a long stream of random requests should > still end up being random IO. > > Al, could you please compare the write throughput from vmstat for the > data=ordered vs data=writeback runs? I would guess the data=ordered one > has a lower overall write throughput. That's what I would have guessed, but it's actually going up 4x fold for mysql from 559mb to 2135mb, while the db-size ends up at 549mb. This may mean that data=ordered isn't buffering redundant writes; or worse. Thanks! -- Al - 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
