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Date: Wed, 21 Nov 2012 20:37:12 +0100 From: Andrea Arcangeli <aarcange@...hat.com> To: Mel Gorman <mgorman@...e.de> Cc: Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Paul Turner <pjt@...gle.com>, Lee Schermerhorn <Lee.Schermerhorn@...com>, Christoph Lameter <cl@...ux.com>, Rik van Riel <riel@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Johannes Weiner <hannes@...xchg.org>, Hugh Dickins <hughd@...gle.com> Subject: Re: [PATCH 00/27] Latest numa/core release, v16 Hi, On Wed, Nov 21, 2012 at 10:38:59AM +0000, Mel Gorman wrote: > HACKBENCH PIPES > 3.7.0 3.7.0 3.7.0 3.7.0 3.7.0 > rc6-stats-v4r12 rc6-schednuma-v16r2rc6-autonuma-v28fastr3 rc6-moron-v4r38 rc6-twostage-v4r38 > Procs 1 0.0320 ( 0.00%) 0.0354 (-10.53%) 0.0410 (-28.28%) 0.0310 ( 3.00%) 0.0296 ( 7.55%) > Procs 4 0.0560 ( 0.00%) 0.0699 (-24.87%) 0.0641 (-14.47%) 0.0556 ( 0.79%) 0.0562 ( -0.36%) > Procs 8 0.0850 ( 0.00%) 0.1084 (-27.51%) 0.1397 (-64.30%) 0.0833 ( 1.96%) 0.0953 (-12.07%) > Procs 12 0.1047 ( 0.00%) 0.1084 ( -3.54%) 0.1789 (-70.91%) 0.0990 ( 5.44%) 0.1127 ( -7.72%) > Procs 16 0.1276 ( 0.00%) 0.1323 ( -3.67%) 0.1395 ( -9.34%) 0.1236 ( 3.16%) 0.1240 ( 2.83%) > Procs 20 0.1405 ( 0.00%) 0.1578 (-12.29%) 0.2452 (-74.52%) 0.1471 ( -4.73%) 0.1454 ( -3.50%) > Procs 24 0.1823 ( 0.00%) 0.1800 ( 1.24%) 0.3030 (-66.22%) 0.1776 ( 2.58%) 0.1574 ( 13.63%) > Procs 28 0.2019 ( 0.00%) 0.2143 ( -6.13%) 0.3403 (-68.52%) 0.2000 ( 0.94%) 0.1983 ( 1.78%) > Procs 32 0.2162 ( 0.00%) 0.2329 ( -7.71%) 0.6526 (-201.85%) 0.2235 ( -3.36%) 0.2158 ( 0.20%) > Procs 36 0.2354 ( 0.00%) 0.2577 ( -9.47%) 0.4468 (-89.77%) 0.2619 (-11.24%) 0.2451 ( -4.11%) > Procs 40 0.2600 ( 0.00%) 0.2850 ( -9.62%) 0.5247 (-101.79%) 0.2724 ( -4.77%) 0.2646 ( -1.75%) > > The number of procs hackbench is running is too low here for a 48-core > machine. It should have been reconfigured but this is better than nothing. > > schednuma and autonuma both show large regressions in the performance here. > I do not investigate why but as there are a number of scheduler changes > it could be anything. Strange, last time I tested hackbench it was perfectly ok, I even had this test shown in some of the pdf. Lately (post my last hackbench run) I disabled the affine wakeups cross-node and pipes use sd_affine wakeups. That could matter for these heavy scheduling tests as it practically disables the _sync in wake_up_interruptible_sync_poll used by the pipe code, if the waker CPU is in a different node than the wakee prev_cpu. I discussed this with Mike and he liked this change IIRC but it's the first thing that should be checked at the light of above regression. > PAGE FAULT TEST > > This is a microbenchmark for page faults. The number of clients are badly ordered > which again, I really should fix but anyway. > > 3.7.0 3.7.0 3.7.0 3.7.0 3.7.0 > rc6-stats-v4r12 rc6-schednuma-v16r2rc6-autonuma-v28fastr3 rc6-moron-v4r38 rc6-twostage-v4r38 > System 1 8.0710 ( 0.00%) 8.1085 ( -0.46%) 8.0925 ( -0.27%) 8.0170 ( 0.67%) 37.3075 (-362.24% > System 10 9.4975 ( 0.00%) 9.5690 ( -0.75%) 12.0055 (-26.41%) 9.5915 ( -0.99%) 9.5835 ( -0.91%) > System 11 9.7740 ( 0.00%) 9.7915 ( -0.18%) 13.4890 (-38.01%) 9.7275 ( 0.48%) 9.6810 ( 0.95%) No real clue on this one as I should look in what the test does. It might be related to THP splits though. I can't imagine anything else because there's nothing at all in autonuma that alters the page faults (except from arming NUMA hinting faults which should be lighter in autonuma than in the other implementation using task work). Chances are the faults are tested by touching bytes at different 4k offsets in the same 2m naturally aligned virtual range. Hugh THP native migration patch will clarify things on the above. > also hope that the concepts of autonuma would be reimplemented on top of > this foundation so we can do a meaningful comparison between different > placement policies. I'll try to help with this to see what could be added from autonuma on top to improve on top your balancenuma foundation. Your current foundation looks ideal for inclusion to me. I noticed you haven't run any single instance specjbb workload, that should be added to the battery of tests. But hey take your time, the amount of data you provided is already very comprehensive and you were so fast. The thing is: single instance and multi instance are totally different beasts. multi instance is all about avoiding NUMA false sharing in the first place (the anti false sharing algorithm becomes a noop), and it has a trivial perfect solution with all cross node traffic guaranteed to stop after converence has been reached for the whole duration of the workload. single instance is all about NUMA false sharing detection and it has no perfect solution and there's no way to fully converge and to stop all cross node traffic. So it's a tradeoff between doing too many CPU/memory spurious migrations (harmful, causes regressions) and doing too few (i.e. not improving at all compared to upstream but not regressing either). autonuma27/28/28fast will perform identical on multi instance loads (i.e. optimal, a few percent away from hard bindings). I was just starting to improve the anti false sharing algorithm in autonuma28/28fast to improve single instance specjbb too (this is why you really need autonuma28 or autonuma28fast to test single instance specjbb and not autonuma27). About THP, normally when I was running benchmarks I was testing these 4 configs: 1) THP on PMD scan on 2) THP on PMD scan off 3) THP off PMD scan on 4) THP off PMD scan off (1 and 2 are practically the same for the autonuma benchmark, because all memory is backed by THP rendering the PMD level hinting faults for 4k pages very unlikely, but I was testing it anyway just in case) THP off is going to hit KVM guests the most and much less host workloads. But even for KVM it's good practice to test with THP off too, to verify the cost of the numa hinting page faults remains very low (the cost is much higher for guests than host because of the vmexists). The KVM benchmark run by IBM was also done in all 4 combinations: THP on/off KSM on/off and showed improvement even for the "No THP" case (btw, things should run much better these days than the old autonuma13). http://dl.dropbox.com/u/82832537/kvm-numa-comparison-0.png -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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