linux-kernel - Re: [PATCH] mm: skip the page buddy block instead of one page

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Message-ID: <520B4A76.8050903@huawei.com>
Date:	Wed, 14 Aug 2013 17:14:30 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Mel Gorman <mgorman@...e.de>
CC:	Andrew Morton <akpm@...ux-foundation.org>, <riel@...hat.com>,
	Minchan Kim <minchan@...nel.org>, <aquini@...hat.com>,
	<linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: skip the page buddy block instead of one page

On 2013/8/14 16:57, Mel Gorman wrote:

> On Wed, Aug 14, 2013 at 12:45:41PM +0800, Xishi Qiu wrote:
>> A large free page buddy block will continue many times, so if the page 
>> is free, skip the whole page buddy block instead of one page.
>>
>> Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
> 
> page_order cannot be used unless zone->lock is held which is not held in
> this path. Acquiring the lock would prevent parallel allocations from the
> buddy allocator (per-cpu allocator would be ok except for refills).  I expect
> it would not be a good tradeoff to acquire the lock just to use page_order.
> 
> Nak.
> 

Oh, you are right, we must hold zone->lock first.

Thanks,
Xishi Qiu
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