linux-kernel - Re: [PATCH] mm, page_alloc: optimize batch count in free_pcppages

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Message-Id: <20130806152357.40031f6702c92ce9f0d10fca@linux-foundation.org>
Date:	Tue, 6 Aug 2013 15:23:57 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Joonsoo Kim <js1304@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH] mm, page_alloc: optimize batch count in
 free_pcppages_bulk()

On Tue,  6 Aug 2013 17:40:40 +0900 Joonsoo Kim <iamjoonsoo.kim@....com> wrote:

> If we use a division operation, we can compute a batch count more closed
> to ideal value. With this value, we can finish our job within
> MIGRATE_PCPTYPES iteration. In addition, batching to free more pages
> may be helpful to cache usage.
> 

hm, maybe.  The .text got 120 bytes larger so the code now will
eject two of someone else's cachelines, which can't be good.  I need
more convincing, please ;)

(bss got larger too - I don't have a clue why this happens).

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