Date: Thu, 15 Aug 2013 23:16:53 +0900
From: Minchan Kim <minchan@kernel.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Xishi Qiu <qiuxishi@huawei.com>, Andrew Morton <akpm@linux-foundation.org>,
        riel@redhat.com, aquini@redhat.com, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: skip the page buddy block instead of one page
Message-ID: <20130815141652.GE8437@gmail.com>
References: <20130814161642.GM2296@suse.de>
 <20130814163921.GC2706@gmail.com>
 <20130814180012.GO2296@suse.de>
 <520C3DD2.8010905@huawei.com>
 <20130815024427.GA2718@gmail.com>
 <520C4EFF.8040305@huawei.com>
 <20130815041736.GA2592@gmail.com>
 <20130815113019.GV2296@suse.de>
 <20130815131935.GA8437@gmail.com>
 <20130815134209.GW2296@suse.de>
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On Thu, Aug 15, 2013 at 02:42:09PM +0100, Mel Gorman wrote:
> On Thu, Aug 15, 2013 at 10:19:35PM +0900, Minchan Kim wrote:
> > > 
> > > Why? We're looking for pages to migrate. If the page is free and at the
> > > maximum order then there is no point searching in the middle of a free
> > > page.
> > 
> > isolate_migratepages_range API works with [low_pfn, end_pfn)
> > and we can't guarantee page_order in normal compaction path
> > so I'd like to limit the skipping by end_pfn conservatively.
> > 
> 
> Fine
> 
> s/MAX_ORDER_NR_PAGES/pageblock_nr_pages/
> 
> and take the min of it and
> 
> low_pfn = min(low_pfn, end_pfn - 1)

True. That was really what I suggested to Xishi.
Only thing we need it is just number to justify for proving the benefit.

Thanks.

-- 
Kind regards,
Minchan Kim
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