linux-kernel - Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged

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Date:	Thu, 07 Apr 2016 13:34:46 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Ebru Akagunduz <ebru.akagunduz@...il.com>, linux-mm@...ck.org
Cc:	hughd@...gle.com, akpm@...ux-foundation.org,
	kirill.shutemov@...ux.intel.com, n-horiguchi@...jp.nec.com,
	aarcange@...hat.com, iamjoonsoo.kim@....com, gorcunov@...nvz.org,
	linux-kernel@...r.kernel.org, mgorman@...e.de, rientjes@...gle.com,
	vbabka@...e.cz, aneesh.kumar@...ux.vnet.ibm.com,
	hannes@...xchg.org, mhocko@...e.cz, boaz@...xistor.com
Subject: Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged

On Thu, 2016-04-07 at 20:28 +0300, Ebru Akagunduz wrote:
> Currently khugepaged makes swapin readahead to improve
> THP collapse rate. This patch checks vm statistics
> to avoid workload of swapin, if unnecessary. So that
> when system under pressure, khugepaged won't consume
> resources to swapin and won't trigger direct reclaim
> when swapin readahead.
> 
> The patch was tested with a test program that allocates
> 800MB of memory, writes to it, and then sleeps. The system
> was forced to swap out all. Afterwards, the test program
> touches the area by writing, it skips a page in each
> 20 pages of the area. When waiting to swapin readahead
> left part of the test, the memory forced to be busy
> doing page reclaim. There was enough free memory during
> test, khugepaged did not swapin readahead due to business.
> 
> Test results:
> 
>                         After swapped out
> -------------------------------------------------------------------
>               | Anonymous | AnonHugePages | Swap      | Fraction  |
> -------------------------------------------------------------------
> With patch    | 0 kB      |  0 kB         | 800000 kB |    %100   |
> -------------------------------------------------------------------
> Without patch | 0 kB      |  0 kB         | 800000 kB |    %100   |
> -------------------------------------------------------------------
> 
>                         After swapped in
> -------------------------------------------------------------------
>               | Anonymous | AnonHugePages | Swap      | Fraction  |
> -------------------------------------------------------------------
> With patch    | 384812 kB | 96256 kB      | 415188 kB |    %25    |
> -------------------------------------------------------------------
> Without patch | 389728 kB | 194560 kB     | 410272 kB |    %49    |
> -------------------------------------------------------------------
> 
> Signed-off-by: Ebru Akagunduz <ebru.akagunduz@...il.com>

Acked-by: Rik van Riel <riel@...hat.com>

-- 
All Rights Reversed.


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