From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757695Ab2HWJIO (ORCPT ); Thu, 23 Aug 2012 05:08:14 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:27501 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751282Ab2HWJIJ (ORCPT ); Thu, 23 Aug 2012 05:08:09 -0400 X-Authority-Analysis: v=2.0 cv=A87uztqG c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=YOaqkLwX9aQA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=7mug7doFhEcA:10 a=meVymXHHAAAA:8 a=3nbZYyFuAAAA:8 a=xcmSSfFKk9aoRfOygJgA:9 a=PUjeQqilurYA:10 a=EvKJbDF4Ut8A:10 a=2E9KpQmbqmkee8fr:21 a=23-myU_EOx042zky:21 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.115.198 Message-ID: <1345712886.5069.41.camel@gandalf.local.home> Subject: Re: [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs From: Steven Rostedt To: Masami Hiramatsu Cc: Yoshihiro YUNOMAE , Amit Shah , Anthony Liguori , Arnd Bergmann , Borislav Petkov , "Franch Ch. Eigler" , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Ingo Molnar , Mathieu Desnoyers , Rusty Russell , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, qemu-devel@nongnu.org, yrl.pp-manager.tt@hitachi.com Date: Thu, 23 Aug 2012 05:08:06 -0400 In-Reply-To: <50359CE9.3000509@hitachi.com> References: <20120822084251.17293.69086.stgit@ltc189.sdl.hitachi.co.jp> <20120822084312.17293.47596.stgit@ltc189.sdl.hitachi.co.jp> <1345642893.5069.31.camel@gandalf.local.home> <50358F13.1030607@hitachi.com> <50359CE9.3000509@hitachi.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.3-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2012-08-23 at 12:00 +0900, Masami Hiramatsu wrote: > (2012/08/23 11:01), Masami Hiramatsu wrote: > > (2012/08/22 22:41), Steven Rostedt wrote: > >> On Wed, 2012-08-22 at 17:43 +0900, Yoshihiro YUNOMAE wrote: > >>> From: Masami Hiramatsu > >>> > >>> Count debugfs/tracing/per_cpu/cpu* to determine the > >>> number of CPUs. > >> > >> I'm curious, do you find that sysconf doesn't return the # of CPUs the > >> system has? > > > > No, sysconf returns the number of hosts CPUs, not guests. > > > >> I've had boxes where the per_cpu/cpu* had more cpus than the > >> box actually holds. But this was a bug in the kernel, not the tool. This > >> change log needs to have rational instead of just explaining what the > >> patch does. > > > > Ah, I see. Hmm, then this should be enabled by a command line > > option or an environment variable. > > Oops, I misunderstood. I'll add more comment for why this > should be tried instead of sysconf. And now that I understand why you are doing this, why not only do this if the TRACE_AGENT or DEBUG_TRACING_DIR is defined. That is, if we are doing it against a bare metal system, then sysconf should suffice, but if we are tracing against a guest, then it should use the tracing directory to determine the buffers. We could add options to override this, but I would think the default should just Do The Right Thing(tm). -- Steve