From: Kalesh Singh <kaleshsingh@google.com>
To: unlisted-recipients:; (no To-header on input)
Cc: surenb@google.com, hridya@google.com, namhyung@kernel.org,
Kalesh Singh <kaleshsingh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>, Shuah Khan <shuah@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Tom Zanussi <zanussi@kernel.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: [PATCH 5/5] tracing/histogram: Document expression arithmetic and constants
Date: Wed, 15 Sep 2021 19:52:49 +0000 [thread overview]
Message-ID: <20210915195306.612966-6-kaleshsingh@google.com> (raw)
In-Reply-To: <20210915195306.612966-1-kaleshsingh@google.com>
Histogram expressions now support division, and multiplication in
addition to the already supported subtraction and addition operators.
Numeric constants can also be used in a hist trigger expressions
or assigned to a variable and used by refernce in an expression.
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
Documentation/trace/histogram.rst | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst
index 533415644c54..e12699abaee8 100644
--- a/Documentation/trace/histogram.rst
+++ b/Documentation/trace/histogram.rst
@@ -1763,6 +1763,20 @@ using the same key and variable from yet another event::
# echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ...' >> event3/trigger
+Expressions support the use of addition, subtraction, multiplication and
+division operators (+-*/).
+
+Note that division by zero always returns -1.
+
+Numeric constants can also be used directly in an expression::
+
+ # echo 'hist:keys=next_pid:timestamp_secs=common_timestamp/1000000 ...' >> event/trigger
+
+or assigned to a variable and referenced in a subsequent expression::
+
+ # echo 'hist:keys=next_pid:us_per_sec=1000000 ...' >> event/trigger
+ # echo 'hist:keys=next_pid:timestamp_secs=common_timestamp/$us_per_sec ...' >> event/trigger
+
2.2.2 Synthetic Events
----------------------
--
2.33.0.309.g3052b89438-goog
next prev parent reply other threads:[~2021-09-15 19:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-15 19:52 [PATCH 0/5] tracing: Extend histogram triggers expression parsing Kalesh Singh
2021-09-15 19:52 ` [PATCH 1/5] tracing: Add support for creating hist trigger variables from literal Kalesh Singh
2021-10-19 20:48 ` Steven Rostedt
2021-10-19 21:21 ` Kalesh Singh
2021-10-19 21:26 ` Steven Rostedt
2021-10-19 21:49 ` Kalesh Singh
2021-09-15 19:52 ` [PATCH 2/5] tracing: Add division and multiplication support for hist triggers Kalesh Singh
2021-10-19 20:45 ` Steven Rostedt
2021-10-19 21:24 ` Kalesh Singh
2021-09-15 19:52 ` [PATCH 3/5] tracing: Fix operator precedence for hist triggers expression Kalesh Singh
2021-09-15 19:52 ` [PATCH 4/5] tracing/selftests: Add tests for hist trigger expression parsing Kalesh Singh
2021-09-15 19:52 ` Kalesh Singh [this message]
2021-09-15 20:09 ` [PATCH 0/5] tracing: Extend histogram triggers " Kalesh Singh
2021-09-30 22:58 ` Namhyung Kim
2021-10-02 0:54 ` Kalesh Singh
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