From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752241AbdKNBVi (ORCPT ); Mon, 13 Nov 2017 20:21:38 -0500 Received: from LGEAMRELO13.lge.com ([156.147.23.53]:59254 "EHLO lgeamrelo13.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751247AbdKNBVe (ORCPT ); Mon, 13 Nov 2017 20:21:34 -0500 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: namhyung@kernel.org X-Original-SENDERIP: 10.177.227.17 X-Original-MAILFROM: namhyung@kernel.org Date: Tue, 14 Nov 2017 10:21:26 +0900 From: Namhyung Kim To: Tom Zanussi Cc: rostedt@goodmis.org, tglx@linutronix.de, mhiramat@kernel.org, vedang.patel@intel.com, bigeasy@linutronix.de, joel.opensrc@gmail.com, joelaf@google.com, mathieu.desnoyers@efficios.com, baohong.liu@intel.com, rajvi.jingar@intel.com, julia@ni.com, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, kernel-team@lge.com Subject: Re: [PATCH v5 24/37] tracing: Add support for 'synthetic' events Message-ID: <20171114012126.GA19630@sejong> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tom, On Thu, Nov 09, 2017 at 02:33:55PM -0600, Tom Zanussi wrote: > Synthetic events are user-defined events generated from hist trigger > variables saved from one or more other events. > > To define a synthetic event, the user writes a simple specification > consisting of the name of the new event along with one or more > variables and their type(s), to the tracing/synthetic_events file. > > For instance, the following creates a new event named 'wakeup_latency' > with 3 fields: lat, pid, and prio: > > # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> \ > /sys/kernel/debug/tracing/synthetic_events > > Reading the tracing/synthetic_events file lists all the > currently-defined synthetic events, in this case the event we defined > above: > > # cat /sys/kernel/debug/tracing/synthetic_events > wakeup_latency u64 lat; pid_t pid; int prio > > At this point, the synthetic event is ready to use, and a histogram > can be defined using it: > > # echo 'hist:keys=pid,prio,lat.log2:sort=pid,lat' >> \ > /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger > > The new event is created under the tracing/events/synthetic/ directory > and looks and behaves just like any other event: > > # ls /sys/kernel/debug/tracing/events/synthetic/wakeup_latency > enable filter format hist id trigger > > Although a histogram can be defined for it, nothing will happen until > an action tracing that event via the trace_synth() function occurs. > The trace_synth() function is very similar to all the other trace_* > invocations spread throughout the kernel, except in this case the > trace_ function and its corresponding tracepoint isn't statically > generated but defined by the user at run-time. > > How this can be automatically hooked up via a hist trigger 'action' is > discussed in a subsequent patch. > > Signed-off-by: Tom Zanussi > --- [SNIP] > +static const char *synth_field_fmt(char *type) > +{ > + const char *fmt = "%llu"; > + > + if (strcmp(type, "s64") == 0) > + fmt = "%lld"; > + else if (strcmp(type, "u64") == 0) > + fmt = "%llu"; > + else if (strcmp(type, "s32") == 0) > + fmt = "%d"; > + else if (strcmp(type, "u32") == 0) > + fmt = "%u"; > + else if (strcmp(type, "s16") == 0) > + fmt = "%d"; > + else if (strcmp(type, "u16") == 0) > + fmt = "%u"; > + else if (strcmp(type, "s8") == 0) > + fmt = "%d"; > + else if (strcmp(type, "u8") == 0) > + fmt = "%u"; > + else if (strcmp(type, "char") == 0) > + fmt = "%d"; > + else if (strcmp(type, "unsigned char") == 0) > + fmt = "%u"; > + else if (strcmp(type, "int") == 0) > + fmt = "%d"; > + else if (strcmp(type, "unsigned int") == 0) > + fmt = "%u"; > + else if (strcmp(type, "long") == 0) > + fmt = "%ld"; > + else if (strcmp(type, "unsigned long") == 0) > + fmt = "%lu"; > + else if (strcmp(type, "pid_t") == 0) > + fmt = "%d"; > + else if (strstr(type, "[") == 0) > + fmt = "%s"; Is it for string? You may want to check it with '!='.. Thanks, Namhyung > + > + return fmt; > +}