From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <439619F9.4030905@yahoo.com.au> Date: Wed, 07 Dec 2005 10:08:41 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [RFC 1/3] Framework for accurate node based statistics References: <20051206182843.19188.82045.sendpatchset@schroedinger.engr.sgi.com> In-Reply-To: <20051206182843.19188.82045.sendpatchset@schroedinger.engr.sgi.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: linux-kernel@vger.kernel.org, Hugh Dickins , linux-mm@kvack.org, Andi Kleen , Marcelo Tosatti List-ID: Christoph Lameter wrote: > [RFC] Framework for accurate node based statistics > > Currently we have various vm counters that are split per cpu. This arrangement > does not allow access to per node statistics that are important to optimize > VM behavior for NUMA architectures. All one can say from the per_cpu > differential variables is how much a certain variable was changed by this cpu > without being able to deduce how many pages in each node are of a certain type. > > This patch introduces a generic framework to allow accurate per node vm > statistics through a large per node and per cpu array. The numbers are > consolidated when the slab drainer runs (every 3 seconds or so) into global > and per node counters. VM functions can then check these statistics by > simply accessing the node specific or global counter. > > A significant problem with this approach is that the statistics are only > accumulated every 3 seconds or so. I have tried various other approaches > but they typically end up with having to add atomic variables to critical > VM paths. I'd be glad if someone else had a bright idea on how to improve > the situation. > Why not have per-node * per-cpu counters? Or even use the current per-zone * per-cpu counters, and work out your node details from there? -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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: email@kvack.org