Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752565AbaKQVpV (ORCPT ); Mon, 17 Nov 2014 16:45:21 -0500 Received: from mga11.intel.com ([192.55.52.93]:47172 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752132AbaKQVpT (ORCPT ); Mon, 17 Nov 2014 16:45:19 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,405,1413270000"; d="scan'208";a="633445357" Date: Mon, 17 Nov 2014 13:45:18 -0800 From: Andi Kleen To: Sukadev Bhattiprolu Cc: Alexander Shishkin , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, Robert Richter , Frederic Weisbecker , Mike Galbraith , Paul Mackerras , Stephane Eranian , kan.liang@intel.com, adrian.hunter@intel.com, markus.t.metzger@intel.com, mathieu.poirier@linaro.org, acme@infradead.org, Peter Zijlstra , Michael Ellerman Subject: Re: [PATCH v8 02/14] perf: Add AUX area to ring buffer for raw data streams Message-ID: <20141117214518.GD10824@tassilo.jf.intel.com> References: <1415972627-37514-1-git-send-email-alexander.shishkin@linux.intel.com> <1415972627-37514-3-git-send-email-alexander.shishkin@linux.intel.com> <20141117212400.GB13111@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141117212400.GB13111@us.ibm.com> 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 On Mon, Nov 17, 2014 at 01:24:00PM -0800, Sukadev Bhattiprolu wrote: > Alexander Shishkin [alexander.shishkin@linux.intel.com] wrote: > | From: Peter Zijlstra > | > | This patch introduces "AUX space" in the perf mmap buffer, intended for > | exporting high bandwidth data streams to userspace, such as instruction > | flow traces. > | > | AUX space is a ring buffer, defined by aux_{offset,size} fields in the > | user_page structure, and read/write pointers aux_{head,tail}, which abide > | by the same rules as data_* counterparts of the main perf buffer. > > The "format" of this raw stream of data can differ across processors > (and architecutres) correct ? i.e the perf tool processing of this > aux data will also differ across processors ? Yes. The main caveat is that you need special handling code in perf. > > Power8 processors support what we call 24x7 counters that collect info > on a large number of events. The current 24x7 support in > (arch/powerpc/perf/hv-24x7.c) currently uses reading one counter at a > time using the pmu->read() interface. > > We are looking for ways to export much larger number of counters through > one pmu->read() or another call. I am trying to see if the hv-24x7 pmu > could use this aux interface and then have/implement a helper in perf > tool to extract the counter values. It's probably only worth it if your amount of data is extremely high and has to be to compressed (like in PT -- no choice, cannot do it otherwise) If your data amounts are more reasonable it will be a lot simpler to stay with the current perf interfaces, even though they have a bit higher overhead. -Andi -- ak@linux.intel.com -- Speaking for myself only -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/