Messages in this thread | | | From | "Huang\, Ying" <> | Subject | Re: [mm, thp] 85b9f46e8e: vm-scalability.throughput -8.7% regression | Date | Wed, 21 Oct 2020 08:41:56 +0800 |
| |
David Rientjes <rientjes@google.com> writes:
> On Tue, 20 Oct 2020, Huang, Ying wrote: > >> >> ========================================================================================= >> >> compiler/cpufreq_governor/kconfig/rootfs/runtime/size/tbox_group/test/testcase/ucode: >> >> gcc-9/performance/x86_64-rhel-8.3/debian-10.4-x86_64-20200603.cgz/300s/1T/lkp-skl-fpga01/lru-shm/vm-scalability/0x2006906 >> >> >> >> commit: >> >> dcdf11ee14 ("mm, shmem: add vmstat for hugepage fallback") >> >> 85b9f46e8e ("mm, thp: track fallbacks due to failed memcg charges separately") >> >> >> >> dcdf11ee14413332 85b9f46e8ea451633ccd60a7d8c >> >> ---------------- --------------------------- >> >> fail:runs %reproduction fail:runs >> >> | | | >> >> 1:4 24% 2:4 perf-profile.calltrace.cycles-pp.sync_regs.error_entry.do_access >> >> 3:4 53% 5:4 perf-profile.calltrace.cycles-pp.error_entry.do_access >> >> 9:4 -27% 8:4 perf-profile.children.cycles-pp.error_entry >> >> 4:4 -10% 4:4 perf-profile.self.cycles-pp.error_entry >> >> %stddev %change %stddev >> >> \ | \ >> >> 477291 -9.1% 434041 vm-scalability.median >> >> 49791027 -8.7% 45476799 vm-scalability.throughput >> >> 223.67 +1.6% 227.36 vm-scalability.time.elapsed_time >> >> 223.67 +1.6% 227.36 vm-scalability.time.elapsed_time.max >> >> 50364 ± 6% +24.1% 62482 ± 10% vm-scalability.time.involuntary_context_switches >> >> 2237 +7.8% 2412 vm-scalability.time.percent_of_cpu_this_job_got >> >> 3084 +18.2% 3646 vm-scalability.time.system_time >> >> 1921 -4.2% 1839 vm-scalability.time.user_time >> >> 13.68 +2.2 15.86 mpstat.cpu.all.sys% >> >> 28535 ± 30% -47.0% 15114 ± 79% numa-numastat.node0.other_node >> >> 142734 ± 11% -19.4% 115000 ± 17% numa-meminfo.node0.AnonPages >> >> 11168 ± 3% +8.8% 12150 ± 5% numa-meminfo.node1.PageTables >> >> 76.00 -1.6% 74.75 vmstat.cpu.id >> >> 3626 -1.9% 3555 vmstat.system.cs >> >> 2214928 ±166% -96.6% 75321 ± 7% cpuidle.C1.usage >> >> 200981 ± 7% -18.0% 164861 ± 7% cpuidle.POLL.time >> >> 52675 ± 3% -16.7% 43866 ± 10% cpuidle.POLL.usage >> >> 35659 ± 11% -19.4% 28754 ± 17% numa-vmstat.node0.nr_anon_pages >> >> 1248014 ± 3% +10.9% 1384236 numa-vmstat.node1.nr_mapped >> >> 2722 ± 4% +10.6% 3011 ± 5% numa-vmstat.node1.nr_page_table_pages >> > >> > I'm not sure that I'm reading this correctly, but I suspect that this just >> > happens because of NUMA: memory affinity will obviously impact >> > vm-scalability.throughput quite substantially, but I don't think the >> > bisected commit can be to be blame. Commit 85b9f46e8ea4 ("mm, thp: track >> > fallbacks due to failed memcg charges separately") simply adds new >> > count_vm_event() calls in a couple areas to track thp fallback due to >> > memcg limits separate from fragmentation. >> > >> > It's likely a question about the testing methodology in general: for >> > memory intensive benchmarks, I suggest it is configured in a manner that >> > we can expect consistent memory access latency at the hardware level when >> > running on a NUMA system. >> >> So you think it's better to bind processes to NUMA node or CPU? But we >> want to use this test case to capture NUMA/CPU placement/balance issue >> too. >> > > No, because binding to a specific socket may cause other performance > "improvements" or "degradations" depending on how fragmented local memory > is, or whether or not it's under memory pressure. Is the system rebooted > before testing so that we have a consistent state of memory availability > and fragmentation across sockets?
Yes. System is rebooted before testing (0day uses kexec to accelerate rebooting).
>> 0day solve the problem in another way. We run the test case >> multiple-times and calculate the average and standard deviation, then >> compare. >> > > Depending on fragmentation or memory availability, any benchmark that > assesses performance may be adversely affected if its results can be > impacted by hugepage backing.
Best Regards, Huang, Ying
| |