Date: Tue, 6 Apr 2010 09:25:36 +0800
From: Shaohua Li <shaohua.li@intel.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
       "Wu, Fengguang" <fengguang.wu@intel.com>
Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio
Message-ID: <20100406012536.GB18672@sli10-desk.sh.intel.com>
References: <20100402181307.6470.A69D9226@jp.fujitsu.com>
 <20100402092441.GA21100@sli10-desk.sh.intel.com>
 <20100404231558.7E00.A69D9226@jp.fujitsu.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20100404231558.7E00.A69D9226@jp.fujitsu.com>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1610
Lines: 32

On Sun, Apr 04, 2010 at 10:19:06PM +0800, KOSAKI Motohiro wrote:
> > On Fri, Apr 02, 2010 at 05:14:38PM +0800, KOSAKI Motohiro wrote:
> > > > > > This patch makes a lot of sense than previous. however I think <1% anon ratio
> > > > > > shouldn't happen anyway because file lru doesn't have reclaimable pages.
> > > > > > <1% seems no good reclaim rate.
> > > > > 
> > > > > Oops, the above mention is wrong. sorry. only 1 page is still too big.
> > > > > because under streaming io workload, the number of scanning anon pages should
> > > > > be zero. this is very strong requirement. if not, backup operation will makes
> > > > > a lot of swapping out.
> > > > Sounds there is no big impact for the workload which you mentioned with the patch.
> > > > please see below descriptions.
> > > > I updated the description of the patch as fengguang suggested.
> > > 
> > > Umm.. sorry, no.
> > > 
> > > "one fix but introduce another one bug" is not good deal. instead, 
> > > I'll revert the guilty commit at first as akpm mentioned.
> > Even we revert the commit, the patch still has its benefit, as it increases
> > calculation precision, right?
> 
> no, you shouldn't ignore the regression case.
I don't think this is serious. In my calculation, there is only 1 page swapped out
for 6G anonmous memory. 1 page should haven't any performance impact.

Thanks,
Shaohua
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/