linux-kernel - Re: [PATCH -V6 RESEND 1/3] numa balancing: Migrate on fault among multiple bound nodes

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Message-ID: <87a6umjcl6.fsf@yhuang-dev.intel.com>
Date:   Thu, 10 Dec 2020 16:21:25 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        Johannes Weiner <hannes@...xchg.org>,
        "Matthew Wilcox \(Oracle\)" <willy@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>, linux-api@...r.kernel.org
Subject: Re: [PATCH -V6 RESEND 1/3] numa balancing: Migrate on fault among multiple bound nodes

"Huang, Ying" <ying.huang@...el.com> writes:

> Peter Zijlstra <peterz@...radead.org> writes:
>
>> On Wed, Dec 02, 2020 at 11:40:54AM +0000, Mel Gorman wrote:
>>> On Wed, Dec 02, 2020 at 04:42:32PM +0800, Huang Ying wrote:
>>> > Now, NUMA balancing can only optimize the page placement among the
>>> > NUMA nodes if the default memory policy is used.  Because the memory
>>> > policy specified explicitly should take precedence.  But this seems
>>> > too strict in some situations.  For example, on a system with 4 NUMA
>>> > nodes, if the memory of an application is bound to the node 0 and 1,
>>> > NUMA balancing can potentially migrate the pages between the node 0
>>> > and 1 to reduce cross-node accessing without breaking the explicit
>>> > memory binding policy.
>>> > 
>>> 
>>> Ok, I think this part is ok and while the test case is somewhat
>>> superficial, it at least demonstrated that the NUMA balancing overhead
>>> did not offset any potential benefit
>>> 
>>> Acked-by: Mel Gorman <mgorman@...e.de>
>>
>> Who do we expect to merge this, me through tip/sched/core or akpm ?
>
> Hi, Peter,
>
> Per my understanding, this is NUMA balancing related, so could go
> through your tree.
>
> BTW: I have just sent -V7 with some small changes per Mel's latest
> comments.
>
> Hi, Andrew,
>
> Do you agree?

So, what's the conclusion here?  Both path works for me.  I will update
2/3 per Alejandro Colomar's comments.  But that's for man-pages only,
not for kernel.  So, we can merge this one into kernel if you think it's
appropriate.

Best Regards,
Huang, Ying