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

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Message-ID: <20130814085711.GK2296@suse.de>
Date:	Wed, 14 Aug 2013 09:57:11 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Xishi Qiu <qiuxishi@...wei.com>
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 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.

-- 
Mel Gorman
SUSE Labs
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