From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752815AbbCPIne (ORCPT ); Mon, 16 Mar 2015 04:43:34 -0400 Received: from mail-wi0-f175.google.com ([209.85.212.175]:38405 "EHLO mail-wi0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750899AbbCPInc (ORCPT ); Mon, 16 Mar 2015 04:43:32 -0400 Date: Mon, 16 Mar 2015 09:43:27 +0100 From: Ingo Molnar To: Namhyung Kim Cc: Arnaldo Carvalho de Melo , Peter Zijlstra , Jiri Olsa , LKML , David Ahern , Minchan Kim , Joonsoo Kim Subject: Re: [RFC/PATCHSET 0/6] perf kmem: Implement page allocation analysis (v1) Message-ID: <20150316084326.GA19820@gmail.com> References: <1426145571-3065-1-git-send-email-namhyung@kernel.org> <20150312104119.GA5978@gmail.com> <20150312145837.GA1398@danjae> <20150316021035.GQ943@sejong> <20150316082642.GA19478@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Namhyung Kim wrote: > Hi Ingo, > > On Mon, Mar 16, 2015 at 5:26 PM, Ingo Molnar wrote: > > > > * Namhyung Kim wrote: > > > >> On Thu, Mar 12, 2015 at 11:58:37PM +0900, Namhyung Kim wrote: > >> > On Thu, Mar 12, 2015 at 11:41:19AM +0100, Ingo Molnar wrote: > >> > > So there's one thing that would be useful: to track pages allocated on > >> > > one node, but freed on another. Those kinds of allocation/free > >> > > patterns are especially expensive and might make sense to visualize. > >> > > >> > I think it can be done easily as slab analysis already contains the info. > >> > >> Hmm.. it seems slab events provide the node info but page events > >> don't. Without it, I don't know which node a page is in so > >> cannot determine such cross-node alloc+free patterns. > > > > Well, but we know the CPU that the allocation occured on, and can > > map the CPU to the node. > > Does it gaurantee that the page always belongs to a same node > allocating cpu is in? I can simply map the page with an node using > cpu info but was not sure whether that's always correct. There's no such guarantee :-( We try to (and generally we succeed in) allocating on the same node, but tooling really needs to know about the memory pressure and other corner cases as well to be dependable. I suspect we need a new trace_mm_page_alloc tracepoint, and a CONFIG_DEBUG_MM_TRACE_PAGE_COMPAT setting to phase out the old tracepoint on new distros? Then we'd also have to track page migration to be able to track the full lifetime of a node in tooling: I think most of the tracepoints are in place, but it has to be checked whether coverage is comprehensive. Thanks, Ingo