Subject: Re: [RFC PATCH] asynchronous page fault.
From: Peter Zijlstra <peterz@infradead.org>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "linux-mm@kvack.org" <linux-mm@kvack.org>,
       "minchan.kim@gmail.com" <minchan.kim@gmail.com>,
       cl@linux-foundation.org
In-Reply-To: <20091228093606.9f2e666c.kamezawa.hiroyu@jp.fujitsu.com>
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	 <20091228093606.9f2e666c.kamezawa.hiroyu@jp.fujitsu.com>
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Date: Mon, 28 Dec 2009 09:55:33 +0100
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On Mon, 2009-12-28 at 09:36 +0900, KAMEZAWA Hiroyuki wrote:
> Hmm ? for single-thread apps ? This patch's purpose is not for lockless
> lookup, it's just a part of work. My purpose is avoiding false-sharing.

False sharing in the sense of the mmap_sem cacheline containing other
variables? How could that ever be a problem for a single threaded
application?

For multi-threaded apps the contention on that cacheline is the largest
issue, and moving it to a vma cacheline doesn't seem like a big
improvement.

You want something much finer grained than vmas, there's lots of apps
working on a single (or very few) vma(s). Leaving you with pretty much
the same cacheline contention. Only now its a different cacheline.

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