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Date: Thu, 9 Dec 2004 15:07:13 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
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To: William Lee Irwin III <wli@holomorphy.com>
cc: Hugh Dickins <hugh@veritas.com>, Linus Torvalds <torvalds@osdl.org>,
       Andrew Morton <akpm@osdl.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Nick Piggin <nickpiggin@yahoo.com.au>, linux-mm@kvack.org,
       linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: page fault scalability patch V12: rss tasklist vs sloppy rss
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On Thu, 9 Dec 2004, William Lee Irwin III wrote:
> Unless the algorithms being compared are properly implemented, they're
> straw men, not valid comparisons.

Sloppy rss left the rss in the section of mm that contained the counters.
So that has a separate cacheline. The idea of putting the atomic ops in a
group was to only have one exclusive cacheline for mmap_sem and the rss.
Which could lead to more bouncing of a single cache line rather than
bouncing multiple cache lines less. But it seems to me that the problem
essentially remains the same if the rss counter is not split.