From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755077Ab2LLUPf (ORCPT ); Wed, 12 Dec 2012 15:15:35 -0500 Received: from one.firstfloor.org ([213.235.205.2]:45705 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754645Ab2LLUPe (ORCPT ); Wed, 12 Dec 2012 15:15:34 -0500 Date: Wed, 12 Dec 2012 21:15:29 +0100 From: Andi Kleen To: Christoph Lameter Cc: Joonsoo Kim , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, andi@firstfloor.org, "Kirill A. Shutemov" Subject: Re: [PATCH] mm: introduce numa_zero_pfn Message-ID: <20121212201529.GD16230@one.firstfloor.org> References: <1355331819-8728-1-git-send-email-js1304@gmail.com> <0000013b90beeb93-87f65a09-0cc3-419f-be26-5271148cb947-000000@email.amazonses.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000013b90beeb93-87f65a09-0cc3-419f-be26-5271148cb947-000000@email.amazonses.com> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > I would expect a processor to fetch the zero page cachelines from the l3 > cache from other sockets avoiding memory transactions altogether. The zero > page is likely in use somewhere so no typically no memory accesses should > occur in a system. It depends on how effectively the workload uses the caches. If something is a cache pig of the L3 cache, then even shareable cache lines may need to be refetched regularly. But if your workloads spends a significant part of its time reading from zero page read only data there is something wrong with the workload. I would do some data profiling first to really prove that is the case. -Andi