linux-kernel - Re: [PATCH 01/17] mm: page_alloc: Do not update zlc unless the zlc is active

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Message-ID: <20140501132520.GC23420@cmpxchg.org>
Date:	Thu, 1 May 2014 09:25:20 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
	Vlastimil Babka <vbabka@...e.cz>, Jan Kara <jack@...e.cz>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/17] mm: page_alloc: Do not update zlc unless the zlc
 is active

On Thu, May 01, 2014 at 09:44:32AM +0100, Mel Gorman wrote:
> The zlc is used on NUMA machines to quickly skip over zones that are full.
> However it is always updated, even for the first zone scanned when the
> zlc might not even be active. As it's a write to a bitmap that potentially
> bounces cache line it's deceptively expensive and most machines will not
> care. Only update the zlc if it was active.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Acked-by: Johannes Weiner <hannes@...xchg.org>
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