On Mon, 2010-08-02 at 20:06 -0400, Ted Ts'o wrote: > On Mon, Aug 02, 2010 at 04:02:32PM -0700, john stultz wrote: > > >From these numbers, it looks like the atomic variables are a minor > > improvement for -rt, but the improvement isn't as drastic as the earlier > > j_state lock change, or the vfs scalability patchset. > > Thanks for doing this quick test run! I was expecting to see a more > dramatic difference, since the j_state_lock patch removed one of the > two global locks in jbd2_journal_stop, and the t_handle_lock patch > removed the second of the two global locks. But I guess the > j_state_lock contention in start_this_handle() is still the dominating factor. > > It's interesting that apparently the latest t_handle_lock patch > doesn't seem to make much difference unless the VFS scalability patch > is also applied. I'm not sure why that makes a difference, but it's > nice to know that with the VFS scalability patch it does seem to help, > even if it doesn't help as much as I had hoped. Well, its likely that with the -rt kernel and without the vfs-scalability changes, we're just burning way more time on vfs lock contention then we are on anything in the ext4 code. Just a theory, but I can try to verify with perf logs if you'd like. > OK, I guess we'll have to start working on the more aggressive > scalability fix ups.... I'm generated mainline results w/ w/o Nick's current vfs-scalability tree. So far any benefit from the atomic patch seems to be < 1% there, but I'm probably not hitting much contention at only 8 cores: 2.6.35-rc6 Throughput 2345.72 MB/sec 8 procs Throughput 1424.11 MB/sec 4 procs Throughput 811.371 MB/sec 2 procs Throughput 444.129 MB/sec 1 procs 2.6.35-rc6 + atomic Throughput 2354.66 MB/sec 8 procs Throughput 1427.64 MB/sec 4 procs Throughput 794.961 MB/sec 2 procs Throughput 443.464 MB/sec 1 procs 2.6.35-rc6-vfs Throughput 2639.04 MB/sec 8 procs Throughput 1583.28 MB/sec 4 procs Throughput 858.337 MB/sec 2 procs Throughput 452.774 MB/sec 1 procs 2.6.35-rc6-vfs + atomic Throughput 2648.42 MB/sec 8 procs Throughput 1586.68 MB/sec 4 procs Throughput 851.545 MB/sec 2 procs Throughput 453.106 MB/sec 1 procs thanks -john -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
