Messages in this thread | | | Subject | Re: [4.17 regression] Performance drop on kernel-4.17 visible on Stream, Linpack and NAS parallel benchmarks | From | Jakub Raček <> | Date | Thu, 7 Jun 2018 13:19:26 +0200 |
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Hi,
On 06/07/2018 01:07 PM, Michal Hocko wrote: > [CCing Mel and MM mailing list] > > On Wed 06-06-18 14:27:32, Jakub Racek wrote: >> Hi, >> >> There is a huge performance regression on the 2 and 4 NUMA node systems on >> stream benchmark with 4.17 kernel compared to 4.16 kernel. Stream, Linpack >> and NAS parallel benchmarks show upto 50% performance drop. >> >> When running for example 20 stream processes in parallel, we see the following behavior: >> >> * all processes are started at NODE #1 >> * memory is also allocated on NODE #1 >> * roughly half of the processes are moved to the NODE #0 very quickly. * >> however, memory is not moved to NODE #0 and stays allocated on NODE #1 >> >> As the result, half of the processes are running on NODE#0 with memory being >> still allocated on NODE#1. This leads to non-local memory accesses >> on the high Remote-To-Local Memory Access Ratio on the numatop charts. >> >> So it seems that 4.17 is not doing a good job to move the memory to the right NUMA >> node after the process has been moved. >> >> ----8<---- >> >> The above is an excerpt from performance testing on 4.16 and 4.17 kernels. >> >> For now I'm merely making sure the problem is reported. > > Do you have numa balancing enabled? >
Yes. The relevant settings are:
kernel.numa_balancing = 1 kernel.numa_balancing_scan_delay_ms = 1000 kernel.numa_balancing_scan_period_max_ms = 60000 kernel.numa_balancing_scan_period_min_ms = 1000 kernel.numa_balancing_scan_size_mb = 256
-- Best regards, Jakub Racek FMK
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