linux-kernel - Re: [PATCH 4/4] numa: introduce numa cling feature

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Message-ID: <c85b5868-150f-7114-18cd-a5e9cd55f406@linux.alibaba.com>
Date:   Mon, 22 Jul 2019 11:44:48 +0800
From:   王贇 <yun.wang@...ux.alibaba.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 4/4] numa: introduce numa cling feature



On 2019/7/12 下午4:58, 王贇 wrote:
[snip]
> 
> I see, we should not override the decision of select_idle_sibling().
> 
> Actually the original design we try to achieve is:
> 
>   let wake affine select the target
>   try find idle sibling of target
>   if got one
> 	pick it
>   else if task cling to prev
> 	pick prev
> 
> That is to consider wake affine superior to numa cling.
> 
> But after rethinking maybe this is not necessary, since numa cling is
> also some kind of strong wake affine hint, actually maybe even a better
> one to filter out the bad cases.
> 
> I'll try change @target instead and give a retest then.

We now leave select_idle_sibling() untouched, instead prevent numa swap
with task cling to dst, and stop wake affine when curr & prev cpu are on
different node and wakee cling to prev.

Retesting show a even better results, benchmark like dbench also show 1%~5%
improvement, not stable but always improved now :-)

Regards,
Michael Wang

> 
> Regards,
> Michael Wang
>