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Date: Fri, 20 Dec 2013 16:44:26 +0000 From: Mel Gorman <mgorman@...e.de> To: Fengguang Wu <fengguang.wu@...el.com> Cc: Alex Shi <alex.shi@...aro.org>, Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Andrew Morton <akpm@...ux-foundation.org>, H Peter Anvin <hpa@...or.com>, Linux-X86 <x86@...nel.org>, Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 0/4] Fix ebizzy performance regression due to X86 TLB range flush v2 On Fri, Dec 20, 2013 at 11:51:43PM +0800, Fengguang Wu wrote: > On Thu, Dec 19, 2013 at 02:34:50PM +0000, Mel Gorman wrote: > > On Wed, Dec 18, 2013 at 03:28:14PM +0800, Fengguang Wu wrote: > > > Hi Mel, > > > > > > I'd like to share some test numbers with your patches applied on top of v3.13-rc3. > > > > > > Basically there are > > > > > > 1) no big performance changes > > > > > > 76628486 -0.7% 76107841 TOTAL vm-scalability.throughput > > > 407038 +1.2% 412032 TOTAL hackbench.throughput > > > 50307 -1.5% 49549 TOTAL ebizzy.throughput > > > > > > > I'm assuming this was an ivybridge processor. > > The test boxes brickland2 and lkp-ib03 are ivybridge; lkp-snb01 is sandybridge. > Ok. > > How many threads were ebizzy tested with? > > The below case has params string "400%-5-30", which means > > nr_threads = 400% * nr_cpu = 4 * 48 = 192 > iterations = 5 > duration = 30 > > v3.13-rc3 eabb1f89905a0c809d13 > --------------- ------------------------- > 50307 ~ 1% -1.5% 49549 ~ 0% lkp-ib03/micro/ebizzy/400%-5-30 > 50307 -1.5% 49549 TOTAL ebizzy.throughput > That is a limited range of threads to test with but ok. > > The memory ranges used by the vm scalability benchmarks are > > probably too large to be affected by the series but I'm guessing. > > Do you mean these lines? > > 3345155 ~ 0% -0.3% 3335172 ~ 0% brickland2/micro/vm-scalability/16G-shm-pread-rand-mt > 33249939 ~ 0% +3.3% 34336155 ~ 1% brickland2/micro/vm-scalability/1T-shm-pread-seq > > The two cases run 128 threads/processes, each accessing randomly/sequentially > a 64GB shm file concurrently. Sorry the 16G/1T prefixes are somehow misleading. > It's ok, the conclusion is still the same. The regions are still too large to be really affected the series. > > I doubt hackbench is doing any flushes and the 1.2% is noise. > > Here are the proc-vmstat.nr_tlb_remote_flush numbers for hackbench: > > 513 ~ 3% +4.3e+16% 2.192e+17 ~85% lkp-nex05/micro/hackbench/800%-process-pipe > 603 ~ 3% +7.7e+16% 4.669e+17 ~13% lkp-nex05/micro/hackbench/800%-process-socket > 6124 ~17% +5.7e+15% 3.474e+17 ~26% lkp-nex05/micro/hackbench/800%-threads-pipe > 7565 ~49% +5.5e+15% 4.128e+17 ~68% lkp-nex05/micro/hackbench/800%-threads-socket > 21252 ~ 6% +1.3e+15% 2.728e+17 ~39% lkp-snb01/micro/hackbench/1600%-threads-pipe > 24516 ~16% +8.3e+14% 2.034e+17 ~53% lkp-snb01/micro/hackbench/1600%-threads-socket > This is a surprise. The differences I can understand because of changes in accounting but not the flushes themselves. The only flushes I would expect are when the process exits and the regions are torn down. The exception would be if automatic NUMA balancing was enabled and this was a NUMA machine. In that case, NUMA hinting faults could be migrating memory and triggering flushes. Could you do something like # perf probe native_flush_tlb_others # cd /sys/kernel/debug/tracing # echo sym-offset > trace_options # echo sym-addr > trace_options # echo stacktrace > trace_options # echo 1 > events/probe/native_flush_tlb_others/enable # cat trace_pipe > /tmp/log and get a breakdown of what the source of these remote flushes are please? > This time, the ebizzy params are refreshed and the test case is > exercised in all our test machines. The results that have changed are: > > v3.13-rc3 eabb1f89905a0c809d13 > --------------- ------------------------- > 873 ~ 0% +0.7% 879 ~ 0% lkp-a03/micro/ebizzy/200%-100-10 > 873 ~ 0% +0.7% 879 ~ 0% lkp-a04/micro/ebizzy/200%-100-10 > 873 ~ 0% +0.8% 880 ~ 0% lkp-a06/micro/ebizzy/200%-100-10 > 49242 ~ 0% -1.2% 48650 ~ 0% lkp-ib03/micro/ebizzy/200%-100-10 > 26176 ~ 0% -1.6% 25760 ~ 0% lkp-sbx04/micro/ebizzy/200%-100-10 > 2738 ~ 0% +0.2% 2744 ~ 0% lkp-t410/micro/ebizzy/200%-100-10 > 80776 -1.2% 79793 TOTAL ebizzy.throughput > No change on lkp-ib03 which I would have expected some difference. Thing is, for ebizzy to notice the number of TLB entries matter. On both machines I tested, the last level TLB had 512 entries. How many entries are on the last level TLB on lkp-ib03? > > I do see a few major regressions like this > > > > > 324497 ~ 0% -100.0% 0 ~ 0% brickland2/micro/vm-scalability/16G-truncate > > > > but I have no idea what the test is doing and whether something happened > > that the test broke that time or if it's something to be really > > concerned about. > > This test case simply creates sparse files, populate them with zeros, > then delete them in parallel. Here $mem is physical memory size 128G, > $nr_cpu is 120. > > for i in `seq $nr_cpu` > do > create_sparse_file $SPARSE_FILE-$i $((mem / nr_cpu)) > cp $SPARSE_FILE-$i /dev/null > done > > for i in `seq $nr_cpu` > do > rm $SPARSE_FILE-$i & > done > In itself, that does not explain why the result was 0 with the series applied. The 3.13-rc3 result was "324497". 324497 what? -- Mel Gorman SUSE Labs -- 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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