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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Wu Fengguang <fengguang.wu@intel.com>
Subject: Re: [RFC][PATCH] mm: remove unnecessary loop inside shrink_inactive_list()
Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton <akpm@linux-foundation.org>,
       Balbir Singh <balbir@linux.vnet.ibm.com>,
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Date: Thu, 27 Aug 2009 09:20:35 +0900 (JST)
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> On Fri, Aug 21, 2009 at 07:09:17PM +0800, KOSAKI Motohiro wrote:
> > 2009/8/20 Wu Fengguang <fengguang.wu@intel.com>:
> > > shrink_inactive_list() won't be called to scan too much pages
> > > (unless in hibernation code which is fine) or too few pages (ie.
> > > batching is taken care of by the callers).  So we can just remove the
> > > big loop and isolate the exact number of pages requested.
> > >
> > > Just a RFC, and a scratch patch to show the basic idea.
> > > Please kindly NAK quick if you don't like it ;)
> > 
> > Hm, I think this patch taks only cleanups. right?
> > if so, I don't find any objection reason.
> 
> Mostly cleanups, but one behavior change here: 
> 
> > > -               nr_taken = sc->isolate_pages(sc->swap_cluster_max,
> > > +               nr_taken = sc->isolate_pages(nr_to_scan,
> > >                             &page_list, &nr_scan, sc->order, mode,
> > >                                zone, sc->mem_cgroup, 0, file);
> 
> The new behavior is to scan exactly the number of pages that
> shrink_zone() or other callers tell it. It won't try to "round it up"
> to 32 pages. This new behavior is in line with shrink_active_list()'s
> current status as well as shrink_zone()'s expectation.
> 
> shrink_zone() may still submit scan requests for <32 pages, which is
> suboptimal. I'll try to eliminate that totally with more patches.

Your explanation seems makes sense.
I'll wait your next spin :)