On Mon, 2010-08-02 at 08:48 -0400, Theodore Ts'o wrote: > By using an atomic_t for t_updates and t_outstanding credits, this > should allow us to not need to take transaction t_handle_lock in > jbd2_journal_stop(). > > Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx> > Cc: John Stultz <johnstul@xxxxxxxxxx> > Cc: Keith Maanthey <kmannth@xxxxxxxxxx> > Cc: Eric Whitney <eric.whitney@xxxxxx> > --- > > It would be interesting to get some quick performance tests with and > without this patch on (a) dbench w/ PREEMPT-RT, (b) Keith's 8-way, and > (c) Eric's 48-core machine. I have some other ideas for how to improve > things in start_this_handle(), but they're going to be tricker, and I > want to do some hard testing using xfstests on a big machine to make > sure this is really safe before I keep going. This has passed light > testing, but I haven't had a chance to do stress tests on a large SMP > machine yet. That'll come later this week, hopefully. So sort of quick and dirty numbers. I'd not trust them too far, but gives a basic feel for how things are doing. So this is dbench #s on an 8-core blade: 1 2 4 8 vfs+j_state lock 401 724 1203 1142 vfs+j_state lock+atomic 408 745 1266 1263 no vfs, no ext4 patches 410 711 1071 434 no vfs, j_state lock 411 714 1113 806 no vfs, j_state lock+atomic 411 723 1149 816 Graphically: http://sr71.net/~jstultz/dbench-scalability/graphs/2.6.33-rt-ext4-atomic/preempt-rt-ext4-dbench.png So the vfs-scalability patchset was reverted from -rt due to some difficult stability issues that were seen in testing. Hopefully we'll be able to sort them out when -rt moves forward to 2.6.35 or later and we can use Nick's more cleaned up current queue rather then my poor forward port of his work from last September. Anyway, I wanted to show how this patch affects dbench numbers on -rt both with and without the vfs-scalability patches and the earlier j_state lock change. The vfs versions use the 2.6.33-rt23 kernel, and the non vfs use the 2.6.33-rt26 kernel. >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. Didn't run into any troubles with this patch in my testing, but again, it was a fairly quick set of runs. 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
