On Mon, Jan 06, 2014 at 04:20:48PM +0800, fengguang.wu@xxxxxxxxx wrote: > Hi Dave, > > We noticed throughput drop in test case > > vm-scalability/300s-lru-file-readtwice (*) > > between v3.11 and v3.12, and it's still low as of v3.13-rc6: > > v3.11 v3.12 v3.13-rc6 > --------------- ------------------------- ------------------------- > 14934707 ~ 0% -48.8% 7647311 ~ 0% -47.6% 7829487 ~ 0% vm-scalability.throughput > ^^ ^^^^^^ > stddev% change% What does this vm-scalability.throughput number mean? > (*) The test case basically does > > truncate -s 135080058880 /tmp/vm-scalability.img > mkfs.xfs -q /tmp/vm-scalability.img > mount -o loop /tmp/vm-scalability.img /tmp/vm-scalability > > nr_cpu=120 > for i in $(seq 1 $nr_cpu) > do > sparse_file=/tmp/vm-scalability/sparse-lru-file-readtwice-$i > truncate $sparse_file -s 36650387592 > dd if=$sparse_file of=/dev/null & > dd if=$sparse_file of=/dev/null & > done So a page cache load of reading 120x36GB files twice concurrently? There's no increase in system time, so it can't be that the shrinkers are running wild. FWIW, I'm at LCA right now, so it's going to be a week before I can look at this, so if you can find any behavioural difference in the shrinkers (e.g. from perf profiles, on different filesystems, etc) I'd appreciate it... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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>