From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 22 Sep 2001 08:36:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 22 Sep 2001 08:36:43 -0400 Received: from u-68-18.karlsruhe.ipdial.viaginterkom.de ([62.180.18.68]:16275 "EHLO dea.linux-mips.net") by vger.kernel.org with ESMTP id ; Sat, 22 Sep 2001 08:36:27 -0400 Date: Sat, 22 Sep 2001 14:28:47 +0200 From: Ralf Baechle To: Davide Libenzi Cc: Rik van Riel , Manfred Spraul , Andrea Arcangeli , linux-kernel@vger.kernel.org, Alan Cox , torvalds@transmeta.com Subject: Re: Purpose of the mm/slab.c changes Message-ID: <20010922142847.A20641@dea.linux-mips.net> In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from davidel@xmailserver.org on Sun, Sep 09, 2001 at 01:58:44PM -0700 X-Accept-Language: de,en,fr Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 09, 2001 at 01:58:44PM -0700, Davide Libenzi wrote: > >> Do You see it as a plus ? > >> The new allocated slab will be very likely written ( w/o regard > >> about the old content ) and an L2 mapping will generate > >> invalidate traffic. > > > > If your invalidates are slower than your RAM, you should > > consider getting another computer. > > You mean a Sun, that uses a separate bus for snooping ? :) > Besides to not under estimate the cache coherency traffic ( that on many CPUs > uses the main memory bus ) there's the fact that the old data eventually > present in L2 won't be used by the new slab user. That's actually what having a slab cache of pre-initialized elements tries to achieve. On anything that uses a MESI-like cache coherence protocol a cached dirty cache line that is written to will not cause any coherency traffic and thus be faster. Ralf -- "Embrace, Enhance, Eliminate" - it worked for the pope, it'll work for Bill.