From mboxrd@z Thu Jan 1 00:00:00 1970 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: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org