From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [RFC PATCH v5 09/10] thermal: add trace events to the power allocator governor Date: Thu, 10 Jul 2014 14:03:50 -0400 Message-ID: <20140710140350.5c75fee9@gandalf.local.home> References: <1405001928-12697-1-git-send-email-javi.merino@arm.com> <1405001928-12697-10-git-send-email-javi.merino@arm.com> <20140710114451.4bbf6785@gandalf.local.home> <20140710162014.GB2622@e104805> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.231]:7905 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751294AbaGJSDx (ORCPT ); Thu, 10 Jul 2014 14:03:53 -0400 In-Reply-To: <20140710162014.GB2622@e104805> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Javi Merino Cc: "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Punit Agrawal , "broonie@kernel.org" , Zhang Rui , Eduardo Valentin , Frederic Weisbecker , Ingo Molnar On Thu, 10 Jul 2014 17:20:14 +0100 "Javi Merino" wrote: > > > > How many CPUs are you saving load_cpu on? A trace event can't be bigger > > than a page. And the data is actually a little less than that with the > > required headers. > > The biggest system I've tested it on is an 8 cpu system (with > NR_CPUS==8). So yes, small and we haven't seen any issues. > > Are you saying that we are siphoning too much data through ftrace? He > find it really valuable to collect information during run and process > it afterwards but I can see how this may not be feasible for systems > with thousands of cpus. Only too much for a single event. Perhaps have the tracepoint post per CPU? Then you wouldn't need that array. -- Steve