On Tue, Jan 15, 2013 at 11:38:14AM -0600, Nathan Zimmer wrote: > > Hello Mel, Hi Nathan, > You helped some time ago with contention in lock_pages on very large boxes. It was Nick Piggin and Jack Steiner that helped the situation within SLES and before my time. I inherited the relevant patches but made relatively few contributions to the effort. > You worked with Jack Steiner on this. Currently I am tasked with improving this > area even more. So I am fishing for any more ideas that would be productive or > worth trying. > > I have some numbers from a 512 machine. > > Linux uvpsw1 3.0.51-0.7.9-default #1 SMP Thu Nov 29 22:12:17 UTC 2012 (f3be9d0) x86_64 x86_64 x86_64 GNU/Linux > 0.166850 > 0.082339 > 0.248428 > 0.081197 > 0.127635 Ok, this looks like a SLES 11 SP2 kernel and so includes some unlock/lock page optimisations. > Linux uvpsw1 3.8.0-rc1-medusa_ntz_clean-dirty #32 SMP Tue Jan 8 16:01:04 CST 2013 x86_64 x86_64 x86_64 GNU/Linux > 0.151778 > 0.118343 > 0.135750 > 0.437019 > 0.120536 > And this is a mainline-ish kernel which doesn't. The main reason I never made an strong effort to push them upstream because the problems are barely observable on any machine I had access to. The unlock page optimisation requires a page flag and while it helps profiles a little, the effects are barely observable on smaller machines (at least since I last checked). One machine it was reported to help dramatically was a 768-way 128 node machine. Forthe 512-way machine you're testing with the figures are marginal. The time to exit is shorter but the amount of time is tiny and very close to noise. I forward ported the relevant patches but on a 48-way machine the results for the same test were well within the noise and the standard deviation was higher. I know you're tasked with improving this area more but what are you using as your example workload? What's the minimum sized machine needed for the optimisations to make a difference? -- Mel Gorman SUSE Labs -- 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>