linux-kernel - Re: [PATCH] mm: raise MemFree by reverting percpu_pagelist

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Message-ID: <4FB0C789.6010107@gmail.com>
Date:	Mon, 14 May 2012 16:51:21 +0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Sasha Levin <levinsasha928@...il.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>,
	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: raise MemFree by reverting percpu_pagelist_fraction
 to 0

On 05/12/2012 12:35 AM, Sasha Levin wrote:
> On Fri, May 11, 2012 at 6:27 PM, Linus Torvalds
> <torvalds@...ux-foundation.org>  wrote:
>> On Fri, May 11, 2012 at 2:01 AM, Minchan Kim<minchan@...nel.org>  wrote:
>>>
>>> I didn't have a time so made quick patch to show just concept.
>>> Not tested and Not consider carefully.
>>> If anyone doesn't oppose, I will send formal patch which will have more beauty code.
>>
>> What's so magical about that '8' *anyway*? We do we have that minimum at all?
>>
>> At the very least, the 8-vs-0 thing needs to be explained.
>
> The '0' acts as an "off" switch.
>
> Once it's on, we reserve 1/x of the pages for the pagelists. I'm not
> sure why 8 was selected in the first place, but I guess it made sense
> that you don't want to reserve 15%+ of your memory for the pagelists.

1/x is not user-friendly, other vm sysctl's use percentage (x%), for 
example, overcommit_ratio.
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