From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261885AbVF0HQ0 (ORCPT ); Mon, 27 Jun 2005 03:16:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261869AbVF0HQX (ORCPT ); Mon, 27 Jun 2005 03:16:23 -0400 Received: from mx2.suse.de ([195.135.220.15]:2188 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S261916AbVF0HN2 (ORCPT ); Mon, 27 Jun 2005 03:13:28 -0400 To: Nick Piggin Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: VFS scalability (was: [rfc] lockless pagecache) References: <42BF9CD1.2030102@yahoo.com.au> <42BFA014.9090604@yahoo.com.au> From: Andi Kleen Date: 27 Jun 2005 09:13:27 +0200 In-Reply-To: <42BFA014.9090604@yahoo.com.au> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin writes: > This is with the filesystem mounted as noatime, so I can't work > out why update_atime is so high on the list. I suspect maybe a > false sharing issue with some other fields. Did all the 64CPUs write to the same file? Then update_atime was just the messenger - it is the first function to read the inode so it eats the cache miss overhead. Maybe adding a prefetch for it at the beginning of sys_read() might help, but then with 64CPUs writing to parts of the inode it will always thrash no matter how many prefetches. -Andi