From patchwork Fri Sep 18 16:26:34 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathieu Poirier X-Patchwork-Id: 7219051 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 12594BEEC1 for ; Fri, 18 Sep 2015 16:31:50 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id EA4F82091E for ; Fri, 18 Sep 2015 16:31:48 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BF1A820903 for ; Fri, 18 Sep 2015 16:31:47 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZcyXp-0004aK-CD; Fri, 18 Sep 2015 16:29:53 +0000 Received: from mail-pa0-f41.google.com ([209.85.220.41]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZcyVr-0001nh-1b for linux-arm-kernel@lists.infradead.org; Fri, 18 Sep 2015 16:27:54 +0000 Received: by pacex6 with SMTP id ex6so55409810pac.0 for ; Fri, 18 Sep 2015 09:27:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=dba9FNWJx/zDrY/KW6gvsq1Smjt/obUdSUQCqXgksbg=; b=Av+blxR143WmkG32VaKIiTT0BHlv4rZBrsgSTFHKW4ktLHSp5HPLsXragO82LdPb5w nhHHFkdhUgL3cYNFPJ1vaoINRTCA4imv7KA4G26fHLLyzpL4GdwaTEEw7sAP+LrFOYgk VtOjEeq5funEvsmtLWL9AKMXhP7IiCViXjKTTxV82S1yMojkc6r42iU+RgKxBnPo9q7T GBYsLAZZvk+DqdfaRLNV/P074fHzx0Qnixxb+vi8REEfw/6rJNrDla615k9vPKyORVm7 TZnxP+Sht2xliG836FZeMkzIT28u6QgLTIgw6QeikVTfq16Y5YJI4WUIA2jpSPBJXVst 4DXA== X-Gm-Message-State: ALoCoQnAmBRkEjOF2nZdji7/2ditZQkvfbvFBx5/2ghbYKz2qvozZR+KGx0njdE+UUI+Zle3wwiE X-Received: by 10.68.225.228 with SMTP id rn4mr8169647pbc.25.1442593650220; Fri, 18 Sep 2015 09:27:30 -0700 (PDT) Received: from t430.cg.shawcable.net ([184.64.168.246]) by smtp.gmail.com with ESMTPSA id la4sm9847027pbc.76.2015.09.18.09.27.28 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 18 Sep 2015 09:27:29 -0700 (PDT) From: Mathieu Poirier To: gregkh@linuxfoundation.org, a.p.zijlstra@chello.nl, alexander.shishkin@linux.intel.com, acme@kernel.org, mingo@redhat.com, corbet@lwn.net Subject: [RFC PATCH 20/20] coresight: updating documentation to reflect integration with perf Date: Fri, 18 Sep 2015 10:26:34 -0600 Message-Id: <1442593594-10665-21-git-send-email-mathieu.poirier@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442593594-10665-1-git-send-email-mathieu.poirier@linaro.org> References: <1442593594-10665-1-git-send-email-mathieu.poirier@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150918_092751_384791_4C537844 X-CRM114-Status: GOOD ( 18.93 ) X-Spam-Score: -2.6 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: al.grant@arm.com, pawel.moll@arm.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, adrian.hunter@intel.com, tor@ti.com, mike.leach@arm.com, zhang.chunyan@linaro.org, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Adding a new section giving information on how coresight has been integrated with the perf subsystem along with a general idea of how to control tracing from the perf tool cmd line. Signed-off-by: Mathieu Poirier --- Documentation/trace/coresight.txt | 116 +++++++++++++++++++++++++++++++++++++- 1 file changed, 113 insertions(+), 3 deletions(-) diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt index 0a5c3290e732..330020082b02 100644 --- a/Documentation/trace/coresight.txt +++ b/Documentation/trace/coresight.txt @@ -193,10 +193,120 @@ the information carried in "THIS_MODULE". How to use ---------- -Before trace collection can start, a coresight sink needs to be identify. -There is no limit on the amount of sinks (nor sources) that can be enabled at +There is two ways to use the coresight framework: 1) using the perf cmd line +tool and 2) interacting directly with the coresight devices using the sysFS +interface. The latter will slowly be faded out as more functionality become +available from the perf cmd line tool but for the time being both are still +supported. The following sections provide details on using both methods. + +1) Using perf framework: + +Coresight tracers like ETM and PTM are represented using the Perf framework's +Performance Monitoring Unit (PMU). As such the perf framework takes charge of +controlling when tracing happens based on when the process(es) of interest are +scheduled. When configure in a system, Coresight PMUs will be listed when +queried by the perf command line tool: + +linaro@linaro-nano:~$ ./perf list pmu + +List of pre-defined events (to be used in -e): + + cs_etm// [Kernel PMU event] + +linaro@linaro-nano:~$ + +Regardless of the amnout ETM/PTM IP block in a system (usually equal to the +amount of processor core), the "cs_etm" PMU will be listed only once. + +Before a trace can be configured and started a Coresight sink needs to be +selected using the sysFS method (see below). This is only temporary until +sink selection can be made from the command line tool. + +linaro@linaro-nano:~$ ls /sys/bus/coresight/devices +20010000.etb 20030000.tpiu 20040000.funnel 2201c000.ptm +2201d000.ptm 2203c000.etm 2203d000.etm 2203e000.etm replicator + +linaro@linaro-nano:~$ echo 1 > /sys/bus/coresight/devices/20010000.etb/enable_sink + +Once a sink has been selected configuring a Coresight PMU works the same way as +any other PMU. As such tracing can happen for a single CPU, a group of CPU, per +thread or a combination of those: + +linaro@linaro-nano:~$ perf record -e cs_etm// --per-thread + +linaro@linaro-nano:~$ perf record -C 0,2-3 -e cs_etm// + +Tracing limited to user and kernel space can also be used to narrow the amount +of collected tracers: + +linaro@linaro-nano:~$ perf record -e cs_etm//u --per-thread + +linaro@linaro-nano:~$ perf record -C 0,2-3 -e cs_etm//k + +As of this writing two ETM/PTM specific options have are available: cycle +accurate and timestamp (please refer to the Embedded Trace Macrocell reference +manual for details on these options). By default both are disabled but using +the "cycacc" and "timestamp" mnemonic within the double '/' will see those +options configure for the upcoming trace run: + +linaro@linaro-nano:~$ perf record -e cs_etm/cycacc/ --per-thread + +linaro@linaro-nano:~$ perf record -C 0,2-3 -e cs_etm/cycacc,timestamp/ + +The Coresight PMUs can be configured to work in "full trace" or "snapshot" mode. +In full trace mode trade acquisition is enable from beginning to end with trace +data being recorded continuously: + +linaro@linaro-nano:~$ perf record -e cs_etm// dd if=/dev/random of=./test.txt bs=1k count=1000 + +Since this can lead to a significant amount of data and that some device are +limited in disk space snapshot mode can be used instead. In snapshot mode +traces are still collected in the ring buffer but not communicated to user +space. The ring buffer is allowed to wrap around, providing the latest +information before an event of interest happens. Significant events are +communicated by sending a USR2 signal to the user space command line tool. +From there the tool will stop trace collection and harvest data from the ring +buffer before re-enabling traces. Snapshot mode can be invoked using '-S' when +launching a trace collection: + +linaro@linaro-nano:~$ perf record -S -e cs_etm// dd if=/dev/random of=./test.txt bs=1k count=1000 + +Trace data collected during trace runs end up in the centennial "perf.data" +file. Trace configuration information necessary for trace decoding are also +embedded in the "perf.data" file. Two new headers, 'PERF_RECORD_AUXTRACE_INFO' +and 'PERF_RECORD_AUXTRACE' have been added to list of event types in order to +find out where the different sections start. + +It is worth nothing that a set of metadata information exists for each tracer +that participated in a trace run. As such if 5 processors have been engaged, +5 set of metadata will be found in the perf.data file. This is to ensure that +tracer decompression tools have all the information they need in order to +process the trace data. + +Metadata information is collected directly from the ETM/PTM management registers +using the sysFS interface. Since there is not way for the perf command line +tool to associate a CPU with a tracer, a symbolic link has been created between +the cs_etm sysFS event directory and each Coresight tracer: + +linaro@linaro-nano:~$ ls /sys/bus/event_source/devices/cs_etm +cpu0 cpu1 cpu2 cpu3 cpu4 format perf_event_mux_interval_ms +power subsystem type uevent + +linaro@linaro-nano:~$ ls /sys/bus/event_source/devices/cs_etm/cpu0/mgmt/ +etmccer etmccr etmcr etmidr etmscr etmtecr1 etmtecr2 +etmteevr etmtraceidr etmtssvr + +2) Using the sysFS interface: + +Most, if not all, configuration registers are made available to users via the +sysFS interface. Until all coresight ETM drivers have been converted to perf, +it will also be possible to start and stop traces from sysFS. + +As with the perf method described above, a coresight sink needs to be identify +before trace collection can commence. Using the sysFS method _only_, there is +no limit on the amount of sinks (nor sources) that can be enabled at any given moment. As a generic operation, all device pertaining to the sink -class will have an "active" entry in sysfs: +class will have an "enable_sink" entry in sysfs: root:/sys/bus/coresight/devices# ls replicator 20030000.tpiu 2201c000.ptm 2203c000.etm 2203e000.etm