Re: [External] Re: [PATCH] cpuset: introduce non-blocking cpuset.mems setting option

[Michal Koutný]

On Wed, Jun 18, 2025 at 10:46:02AM +0800, Zhongkun He <hezhongkun.hzk@xxxxxxxxxxxxx> wrote:
> It is unnecessary to adjust memory affinity periodically from userspace,
> as it is a costly operation.

It'd be always costly when there's lots of data to migrate.

> Instead, we need to shrink cpuset.mems to explicitly specify the NUMA
> node from which newly allocated pages should come, and migrate the
> pages once in userspace slowly  or adjusted by numa balance.

IIUC, the issue is that there's no set_mempolicy(2) for 3rd party
threads (it only operates on current) OR that the migration path should
be optimized to avoid those latencies -- do you know what is the
contention point?

Thanks,
Michal

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