From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261861AbVGEPZL (ORCPT ); Tue, 5 Jul 2005 11:25:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261838AbVGEPZL (ORCPT ); Tue, 5 Jul 2005 11:25:11 -0400 Received: from 66-23-228-155.clients.speedfactory.net ([66.23.228.155]:22472 "EHLO kevlar.burdell.org") by vger.kernel.org with ESMTP id S261881AbVGEPNb (ORCPT ); Tue, 5 Jul 2005 11:13:31 -0400 Date: Tue, 5 Jul 2005 11:11:19 -0400 From: Sonny Rao To: "Chen, Kenneth W" Cc: "'Christoph Lameter'" , "'Badari Pulavarty'" , "'Nick Piggin'" , Lincoln Dale , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [rfc] lockless pagecache Message-ID: <20050705151119.GA12279@kevlar.burdell.org> References: <200506271942.j5RJgig23410@unix-os.sc.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200506271942.j5RJgig23410@unix-os.sc.intel.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 27, 2005 at 12:42:44PM -0700, Chen, Kenneth W wrote: > Christoph Lameter wrote on Monday, June 27, 2005 12:23 PM > > On Mon, 27 Jun 2005, Chen, Kenneth W wrote: > > > I don't recall seeing tree_lock to be a problem for DSS workload either. > > > > I have seen the tree_lock being a problem a number of times with large > > scale NUMA type workloads. > > I totally agree! My earlier posts are strictly referring to industry > standard db workloads (OLTP, DSS). I'm not saying it's not a problem > for everyone :-) Obviously you just outlined a few .... I'm a bit late to the party here (was gone on vacation), but I do have profiles from DSS workloads using page-cache rather than O_DIRECT and I do see spin_lock_irq() in the profiles which I'm pretty certain are locks spinning for access to the radix_tree. I'll talk about it a bit more up in Ottawa but here's the top 5 on my profile (sorry don't have the number of ticks at the momement): 1. dedicated_idle (waiting for I/O) 2. __copy_tofrom_user 3. radix_tree_delete 4. _spin_lock_irq 5. __find_get_block So, yes, if the page-cache is used in a DSS workload then one will see the tree-lock. BTW, this was on a PPC64 machine w/ a fairly small NUMA factor. Sonny