Re: [RFC] autonuma: Support to scan page table asynchronously

[Huang\, Ying]

Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes:

> On Tue, Apr 14, 2020 at 01:06:46PM +0100, Mel Gorman wrote:
>> While it's just an opinion, my preference would be to focus on reducing
>> the cost and amount of scanning done -- particularly for threads.
>
> This; I really don't believe in those back-charging things, esp. since
> not having cgroups or having multiple applications in a single cgroup is
> a valid setup.

Technically, it appears possible to back-charge the CPU time to the
process/thread directly (not the cgroup).

> Another way to reduce latency spikes is to decrease both
> sysctl_numa_balancing_scan_delay and sysctl_numa_balancing_scan_size.
> Then you do more smaller scans. By scanning more often you reduce the
> contrast, by reducing the size you lower the max latency.

Yes.  This can reduce latency spikes.

Best Regards,
Huang, Ying

> And this is all assuming you actually want numa balancing for this
> process.