From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262542AbVG2KOZ (ORCPT ); Fri, 29 Jul 2005 06:14:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262555AbVG2KLp (ORCPT ); Fri, 29 Jul 2005 06:11:45 -0400 Received: from mx1.elte.hu ([157.181.1.137]:463 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S262554AbVG2KJI (ORCPT ); Fri, 29 Jul 2005 06:09:08 -0400 Date: Fri, 29 Jul 2005 12:08:13 +0200 From: Ingo Molnar To: Eric Dumazet Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slab.c : prefetchw the start of new allocated objects Message-ID: <20050729100813.GA16129@elte.hu> References: <42E6C8DB.4090608@earthlink.net> <42E7A8D8.1030809@earthlink.net> <20050729014150.6e97dfd2.akpm@osdl.org> <42E9F145.7040302@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42E9F145.7040302@cosmosbay.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Eric Dumazet wrote: > local_irq_restore(save_flags); > objp = cache_alloc_debugcheck_after(cachep, flags, objp, __builtin_return_address(0)); > + prefetchw(objp); > return objp; the idea is good, but i'd suggest to do the prefetchw a bit earlier, right where we calculate objp. Furthermore, it might make sense to only trigger the prefetchw in the alloc-miss (non-per-CPU cache) case. There it's almost surely a win, in the per-CPU cache case it's not always. Ingo