linux-kernel - Re: [PATCH 3/4] numa: introduce numa group per task group

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Date:   Thu, 11 Jul 2019 16:10:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     王贇 <yun.wang@...ux.alibaba.com>
Cc:     hannes@...xchg.org, mhocko@...nel.org, vdavydov.dev@...il.com,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, mcgrof@...nel.org, keescook@...omium.org,
        linux-fsdevel@...r.kernel.org, cgroups@...r.kernel.org,
        Mel Gorman <mgorman@...e.de>, riel@...riel.com
Subject: Re: [PATCH 3/4] numa: introduce numa group per task group

On Wed, Jul 03, 2019 at 11:32:32AM +0800, 王贇 wrote:
> By tracing numa page faults, we recognize tasks sharing the same page,
> and try pack them together into a single numa group.
> 
> However when two task share lot's of cache pages while not much
> anonymous pages, since numa balancing do not tracing cache page, they
> have no chance to join into the same group.
> 
> While tracing cache page cost too much, we could use some hints from

I forgot; where again do we skip shared pages? task_numa_work() doesn't
seem to skip file vmas.

> userland and cpu cgroup could be a good one.
> 
> This patch introduced new entry 'numa_group' for cpu cgroup, by echo
> non-zero into the entry, we can now force all the tasks of this cgroup
> to join the same numa group serving for task group.
> 
> In this way tasks are more likely to settle down on the same node, to
> share closer cpu cache and gain benefit from NUMA on both file/anonymous
> pages.
> 
> Besides, when multiple cgroup enabled numa group, they will be able to
> exchange task location by utilizing numa migration, in this way they
> could achieve single node settle down without breaking load balance.

I dislike cgroup only interfaces; it there really nothing else we could
use for this?