From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5FFFCC636CA for ; Wed, 21 Jul 2021 15:04:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4354660FF1 for ; Wed, 21 Jul 2021 15:04:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239504AbhGUOXc (ORCPT ); Wed, 21 Jul 2021 10:23:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:56840 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239478AbhGUOUe (ORCPT ); Wed, 21 Jul 2021 10:20:34 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3F46A6120E; Wed, 21 Jul 2021 15:01:00 +0000 (UTC) Date: Wed, 21 Jul 2021 11:00:53 -0400 From: Steven Rostedt To: LKML Cc: Tom Zanussi , Masami Hiramatsu , Namhyung Kim , Ingo Molnar , Andrew Morton Subject: [PATCH v3] tracing/histogram: Rename "cpu" to "common_cpu" Message-ID: <20210721110053.26b4f641@oasis.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" Currently the histogram logic allows the user to write "cpu" in as an event field, and it will record the CPU that the event happened on. The problem with this is that there's a lot of events that have "cpu" as a real field, and using "cpu" as the CPU it ran on, makes it impossible to run histograms on the "cpu" field of events. For example, if I want to have a histogram on the count of the workqueue_queue_work event on its cpu field, running: ># echo 'hist:keys=cpu' > events/workqueue/workqueue_queue_work/trigger Gives a misleading and wrong result. Change the command to "common_cpu" as no event should have "common_*" fields as that's a reserved name for fields used by all events. And this makes sense here as common_cpu would be a field used by all events. Now we can even do: ># echo 'hist:keys=common_cpu,cpu if cpu < 100' > events/workqueue/workqueue_queue_work/trigger ># cat events/workqueue/workqueue_queue_work/hist # event histogram # # trigger info: hist:keys=common_cpu,cpu:vals=hitcount:sort=hitcount:size=2048 if cpu < 100 [active] # { common_cpu: 0, cpu: 2 } hitcount: 1 { common_cpu: 0, cpu: 4 } hitcount: 1 { common_cpu: 7, cpu: 7 } hitcount: 1 { common_cpu: 0, cpu: 7 } hitcount: 1 { common_cpu: 0, cpu: 1 } hitcount: 1 { common_cpu: 0, cpu: 6 } hitcount: 2 { common_cpu: 0, cpu: 5 } hitcount: 2 { common_cpu: 1, cpu: 1 } hitcount: 4 { common_cpu: 6, cpu: 6 } hitcount: 4 { common_cpu: 5, cpu: 5 } hitcount: 14 { common_cpu: 4, cpu: 4 } hitcount: 26 { common_cpu: 0, cpu: 0 } hitcount: 39 { common_cpu: 2, cpu: 2 } hitcount: 184 Now for backward compatibility, I added a trick. If "cpu" is used, and the field is not found, it will fall back to "common_cpu" and work as it did before. This way, it will still work for old programs that use "cpu" to get the actual CPU, but if the event has a "cpu" as a field, it will get that event's "cpu" field, which is probably what it wants anyway. I updated the tracefs/README to include documentation about both the common_timestamp and the common_cpu. This way, if that text is present in the README, then an application can know that common_cpu is supported over just plain "cpu". Cc: stable@vger.kernel.org Fixes: 8b7622bf94a44 ("tracing: Add cpu field for hist triggers") Signed-off-by: Steven Rostedt (VMware) --- Changes since v2: compile tested :-p and found I missed a '"' in the README. Documentation/trace/histogram.rst | 2 +- kernel/trace/trace.c | 4 ++++ kernel/trace/trace_events_hist.c | 22 ++++++++++++++++------ 3 files changed, 21 insertions(+), 7 deletions(-) diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index b71e09f745c3..f99be8062bc8 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -191,7 +191,7 @@ Documentation written by Tom Zanussi with the event, in nanoseconds. May be modified by .usecs to have timestamps interpreted as microseconds. - cpu int the cpu on which the event occurred. + common_cpu int the cpu on which the event occurred. ====================== ==== ======================================= Extended error information diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 14f56e9fa001..e6074040c977 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5619,6 +5619,10 @@ static const char readme_msg[] = "\t [:name=histname1]\n" "\t [:.]\n" "\t [if ]\n\n" + "\t Note, special fields can be used as well:\n" + "\t common_timestamp - to record current timestamp\n" + "\t common_cpu - to record the CPU the event happened on\n" + "\n" "\t When a matching event is hit, an entry is added to a hash\n" "\t table using the key(s) and value(s) named, and the value of a\n" "\t sum called 'hitcount' is incremented. Keys and values\n" diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 16a9dfc9fffc..34325f41ebc0 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1111,7 +1111,7 @@ static const char *hist_field_name(struct hist_field *field, field->flags & HIST_FIELD_FL_ALIAS) field_name = hist_field_name(field->operands[0], ++level); else if (field->flags & HIST_FIELD_FL_CPU) - field_name = "cpu"; + field_name = "common_cpu"; else if (field->flags & HIST_FIELD_FL_EXPR || field->flags & HIST_FIELD_FL_VAR_REF) { if (field->system) { @@ -1991,14 +1991,24 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file, hist_data->enable_timestamps = true; if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS) hist_data->attrs->ts_in_usecs = true; - } else if (strcmp(field_name, "cpu") == 0) + } else if (strcmp(field_name, "common_cpu") == 0) *flags |= HIST_FIELD_FL_CPU; else { field = trace_find_event_field(file->event_call, field_name); if (!field || !field->size) { - hist_err(tr, HIST_ERR_FIELD_NOT_FOUND, errpos(field_name)); - field = ERR_PTR(-EINVAL); - goto out; + /* + * For backward compatibility, if field_name + * was "cpu", then we treat this the same as + * common_cpu. + */ + if (strcmp(field_name, "cpu") == 0) { + *flags |= HIST_FIELD_FL_CPU; + } else { + hist_err(tr, HIST_ERR_FIELD_NOT_FOUND, + errpos(field_name)); + field = ERR_PTR(-EINVAL); + goto out; + } } } out: @@ -5085,7 +5095,7 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field) seq_printf(m, "%s=", hist_field->var.name); if (hist_field->flags & HIST_FIELD_FL_CPU) - seq_puts(m, "cpu"); + seq_puts(m, "common_cpu"); else if (field_name) { if (hist_field->flags & HIST_FIELD_FL_VAR_REF || hist_field->flags & HIST_FIELD_FL_ALIAS) -- 2.31.1