On Thu, Jun 07, 2012 at 11:45:04AM +0200, Jan Kara wrote: [..] > > Instead of above, I modified sync_file_range() to call > > __filemap_fdatawrite_range(WB_SYNC_NONE) and I do see now ASYNC writes > > showing up at elevator. > > > > With 4 processes doing sync_file_range() now, firefox start time test > > clocks around 18-19 seconds which is better than 30-35 seconds of 4 > > processes doing buffered writes. And system looks pretty good from > > interactivity point of view. > So do you have any idea why is that? Do we drive shallower queues? Also > how does speed of the writers compare to the speed with normal buffered > writes + fsync (you'd need fsync for sync_file_range writers as well to > make comparison fair)? Ok, I did more tests and few odd things I noticed. - Results are varying a lot. Sometimes with write+flush workload also firefox launched fast. So now it is hard to conclude things. - For some reason I had nr_requests as 16K on my root drive. I have no idea who is setting it. Once I set it to 128, then firefox with write+flush workload performs much better and launch time are similar to sync_file_range. - I tried to open new windows in firefox and browse web, load new websites. I would say sync_file_range() feels little better but I don't have any logical explanation and can't conclude anything yet by looking at traces. I am continuing to stare though. So in summary, at this point of time I really can't conclude that using sync_file_range() with ASYNC request is providing better latencies in my setup. I will keept at it though and if I notice something new, will write back. Thanks Vivek -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>