From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio
Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton <akpm@linux-foundation.org>,
       Shaohua Li <shaohua.li@intel.com>,
       "Wu, Fengguang" <fengguang.wu@intel.com>,
       "linux-mm@kvack.org" <linux-mm@kvack.org>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
In-Reply-To: <4BBF9B34.5040909@redhat.com>
References: <20100409142057.be0ce5af.akpm@linux-foundation.org> <4BBF9B34.5040909@redhat.com>
Message-Id: <20100413102641.4A18.A69D9226@jp.fujitsu.com>
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Date: Tue, 13 Apr 2010 10:30:34 +0900 (JST)
Sender: linux-kernel-owner@vger.kernel.org
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> 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@redhat.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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