Re: [4.17 regression] Performance drop on kernel-4.17 visible on Stream, Linpack and NAS parallel benchmarks

[Jakub RaÄek]

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