linux-kernel - Re: [RFC] mm/vmscan.c: avoid possible long latency caused by too_many

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Date:   Thu, 22 Apr 2021 14:02:57 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Yu Zhao <yuzhao@...gle.com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Huang Ying <ying.huang@...el.com>,
        Michal Hocko <mhocko@...e.com>, wfg@...l.ustc.edu.cn,
        Shakeel Butt <shakeelb@...gle.com>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [RFC] mm/vmscan.c: avoid possible long latency caused by
 too_many_isolated()



On 4/22/21 1:57 PM, Yu Zhao wrote:
> On Thu, Apr 22, 2021 at 2:38 PM Tim Chen <tim.c.chen@...ux.intel.com> wrote:
>>
>>
>>
>> On 4/22/21 1:30 PM, Yu Zhao wrote:
>>>
>>> HZ/10 is purely arbitrary but that's ok because we assume normally
>>> nobody hits it. If you do often, we need to figure out why and how not
>>> to hit it so often.
>>>
>>
>> Perhaps Zhengjun can test the proposed fix in his test case to see if the timeout value
>> makes any difference.
> 
> Shakeel has another test to stress page reclaim to a point that the
> kernel can livelock for two hours because of a large number of
> concurrent reclaimers stepping on each other. He might be able to
> share that test with you in case you are interested.

That will be great.  Yes, we are interested to have the test.

Tim

> 
> Also it's Hugh who first noticed that migration can isolate many pages
> and in turn block page reclaim. He might be able to help too, in case
> you are interested in the interaction between migration and page
> reclaim.
> 
> Thanks.
>