Re: [Question] Mlocked count will not be decreased

From	Yisheng Xie <xieyisheng1@huawei.com>
Newsgroups	linux.kernel
Subject	Re: [Question] Mlocked count will not be decreased
Date	2017-05-25 03:10 +0200
Message-ID	<tKPrP-1o3-7@gated-at.bofh.it> (permalink)
References	<tKjih-4vy-9@gated-at.bofh.it> <tKzZN-8mT-37@gated-at.bofh.it> <tKBRT-18H-7@gated-at.bofh.it> <tKCXE-1Q9-15@gated-at.bofh.it> <tKD7j-1Uh-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Vlastimil,

Thanks for comment.
On 2017/5/24 19:52, Vlastimil Babka wrote:
> On 05/24/2017 01:38 PM, Xishi Qiu wrote:
>>>
>>> Race condition with what? Who else would isolate our pages?
>>>
>>
>> Hi Vlastimil,
>>
>> I find the root cause, if the page was not cached on the current cpu,
>> lru_add_drain() will not push it to LRU. So we should handle fail
>> case in mlock_vma_page().
> 
> Yeah that would explain it.
> 
>> follow_page_pte()
>> 		...
>> 		if (page->mapping && trylock_page(page)) {
>> 			lru_add_drain();  /* push cached pages to LRU */
>> 			/*
>> 			 * Because we lock page here, and migration is
>> 			 * blocked by the pte's page reference, and we
>> 			 * know the page is still mapped, we don't even
>> 			 * need to check for file-cache page truncation.
>> 			 */
>> 			mlock_vma_page(page);
>> 			unlock_page(page);
>> 		}
>> 		...
>>
>> I think we should add yisheng's patch, also we should add the following change.
>> I think it is better than use lru_add_drain_all().
> 
> I agree about yisheng's fix (but v2 didn't address my comments). I don't
> think we should add the hunk below, as that deviates from the rest of
> the design.
> 
Sorry, I have sent the patch before your comment. Anyway I will send another version
as your suggestion.

Thanks
Yisheng Xie

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[Question] Mlocked count will not be decreased Kefeng Wang <wangkefeng.wang@huawei.com> - 2017-05-23 16:50 +0200
  Re: [Question] Mlocked count will not be decreased Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-05-24 00:10 +0200
  Re: [Question] Mlocked count will not be decreased Yisheng Xie <xieyisheng1@huawei.com> - 2017-05-24 10:40 +0200
    Re: [Question] Mlocked count will not be decreased Kefeng Wang <wangkefeng.wang@huawei.com> - 2017-05-24 11:00 +0200
    Re: [Question] Mlocked count will not be decreased Vlastimil Babka <vbabka@suse.cz> - 2017-05-24 12:40 +0200
      Re: [Question] Mlocked count will not be decreased Vlastimil Babka <vbabka@suse.cz> - 2017-05-24 12:50 +0200
      Re: [Question] Mlocked count will not be decreased Xishi Qiu <qiuxishi@huawei.com> - 2017-05-24 13:00 +0200
      Re: [Question] Mlocked count will not be decreased Xishi Qiu <qiuxishi@huawei.com> - 2017-05-24 13:50 +0200
        Re: [Question] Mlocked count will not be decreased Vlastimil Babka <vbabka@suse.cz> - 2017-05-24 14:00 +0200
          Re: [Question] Mlocked count will not be decreased Xishi Qiu <qiuxishi@huawei.com> - 2017-05-24 14:20 +0200
            Re: [Question] Mlocked count will not be decreased Vlastimil Babka <vbabka@suse.cz> - 2017-05-24 15:20 +0200
              Re: [Question] Mlocked count will not be decreased Xishi Qiu <qiuxishi@huawei.com> - 2017-05-25 03:20 +0200
                Re: [Question] Mlocked count will not be decreased Vlastimil Babka <vbabka@suse.cz> - 2017-05-25 08:20 +0200
          Re: [Question] Mlocked count will not be decreased Yisheng Xie <xieyisheng1@huawei.com> - 2017-05-25 03:10 +0200

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