linux-kernel - Re: [PATCH] mm/page_alloc: return 0 in case this node has no page within the zone

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Message-ID: <20170207150708.GA31837@WeideMBP.lan>
Date:   Tue, 7 Feb 2017 23:07:08 +0800
From:   Wei Yang <richard.weiyang@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Wei Yang <richard.weiyang@...il.com>, vbabka@...e.cz,
        mgorman@...hsingularity.net, mhocko@...e.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page_alloc: return 0 in case this node has no page
 within the zone

On Mon, Feb 06, 2017 at 03:29:32PM -0800, Andrew Morton wrote:
>On Mon,  6 Feb 2017 23:43:14 +0800 Wei Yang <richard.weiyang@...il.com> wrote:
>
>> The whole memory space is divided into several zones and nodes may have no
>> page in some zones. In this case, the __absent_pages_in_range() would
>> return 0, since the range it is searching for is an empty range.
>> 
>> Also this happens more often to those nodes with higher memory range when
>> there are more nodes, which is a trend for future architectures.
>> 
>> This patch checks the zone range after clamp and adjustment, return 0 if
>> the range is an empty range.
>
>What are the user-visible runtime effects of this change?

Hmm, for users they may not "see" the effect, while it will save some time in
case there is no overlap between the zone and node.

-- 
Wei Yang
Help you, Help me

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