linux-kernel - Re: [PATCH]vmscan: handle underflow for get_scan

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Message-Id: <20100413102641.4A18.A69D9226@jp.fujitsu.com>
Date:	Tue, 13 Apr 2010 10:30:34 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shaohua Li <shaohua.li@...el.com>,
	"Wu, Fengguang" <fengguang.wu@...el.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio

> On 04/09/2010 05:20 PM, Andrew Morton wrote:
> 
> > Come to that, it's not obvious that we need this in 2.6.34 either.  What
> > is the user-visible impact here?
> 
> I suspect very little impact, especially during workloads
> where we can just reclaim clean page cache at DEF_PRIORITY.
> FWIW, the patch looks good to me, so:
> 
> Acked-by: Rik van Riel <riel@...hat.com>
> 

I'm surprised this ack a bit. Rik, do you have any improvement plan about
streaming io detection logic?
I think the patch have a slightly marginal benefit, it help to <1% scan
ratio case. but it have big regression, it cause streaming io (e.g. backup
operation) makes tons swap.

So, I thought we sould do either,
1) drop this one
2) merge to change stream io detection logic improvement at first, and
   merge this one at second.

Am i missing something?


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