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SubjectRe: [4.17 regression] Performance drop on kernel-4.17 visible on Stream, Linpack and NAS parallel benchmarks
On Wed, Jun 6, 2018 at 2:34 PM, Rafael J. Wysocki <rafael@kernel.org> wrote:
> On Wed, Jun 6, 2018 at 2:27 PM, Jakub Racek <jracek@redhat.com> 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.
>
> OK, and why do you think that it is related to ACPI?

In any case, we need more information here.

Thanks,
Rafael

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