Re: [PATCH v4 0/2] refactor sqthread cpu binding logic

["Michal Koutný" <mkoutny@suse.com>]

Hello Hao.

On Wed, Sep 01, 2021 at 08:43:20PM +0800, Hao Xu <haoxu@linux.alibaba.com> wrote:
> This patchset is to enhance sqthread cpu binding logic, we didn't
> consider cgroup setting before. In container environment, theoretically
> sqthread is in its container's task group, it shouldn't occupy cpu out
> of its container.

I see in the discussions that there's struggle to make
set_cpus_allowed_ptr() do what's intended under the given constraints.

IIUC, set_cpus_allowed_ptr() is conventionally used for kernel threads
[1]. But does the sqthread fall into this category? You want to have it
_directly_ associated with a container and its cgroups. It looks to me
more like a userspace thread (from this perspective, not literally). Or
is there a different intention?

It seems to me that reusing the sched_setaffinity() (with all its
checks and race pains/solutions) would be a more universal approach.
(I don't mean calling sched_setaffinity() directly, some parts would
need to be factored separately to this end.) WDYT?


Regards,
Michal

[1] Not only spending their life in kernel but providing some
delocalized kernel service.