On Tue, 2009-01-13 at 18:21 +0100, Peter Zijlstra wrote: > On Tue, 2009-01-13 at 08:49 -0800, Linus Torvalds wrote: > > > > So do a v10, and ask people to test. > > --- > Subject: mutex: implement adaptive spinning > From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > Date: Mon Jan 12 14:01:47 CET 2009 > > Change mutex contention behaviour such that it will sometimes busy wait on > acquisition - moving its behaviour closer to that of spinlocks. > I've spent a bunch of time on this one, and noticed earlier today that I still had bits of CONFIG_FTRACE compiling. I wasn't actually tracing anything, but it seems to have had a big performance hit. The bad news is the simple spin got much much faster, dbench 50 coming in at 1282MB/s instead of 580MB/s. (other benchmarks give similar results) v10 is better that not spinning, but its in the 5-10% range. So, I've been trying to find ways to close the gap, just to understand exactly where it is different. If I take out: /* * If there are pending waiters, join them. */ if (!list_empty(&lock->wait_list)) break; v10 pops dbench 50 up to 1800MB/s. The other tests soundly beat my spinning and aren't less fair. But clearly this isn't a good solution. I tried a few variations, like only checking the wait list once before looping, which helps some. Are there other suggestions on better tuning options? (I retested v7 and see similar results) -chris -- 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
