From: Steven Rostedt <rostedt@goodmis.org>
To: Kalesh Singh <kaleshsingh@google.com>
Cc: surenb@google.com, hridya@google.com, namhyung@kernel.org,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Shuah Khan <shuah@kernel.org>, Tom Zanussi <zanussi@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH 1/5] tracing: Add support for creating hist trigger variables from literal
Date: Tue, 19 Oct 2021 16:48:34 -0400 [thread overview]
Message-ID: <20211019164834.465b2a53@gandalf.local.home> (raw)
In-Reply-To: <20210915195306.612966-2-kaleshsingh@google.com>
On Wed, 15 Sep 2021 19:52:45 +0000
Kalesh Singh <kaleshsingh@google.com> wrote:
> Currently hist trigger expressions don't support the use of numeric
> literals:
> e.g. echo 'hist:keys=common_pid:x=$y-1234'
> --> is not valid expression syntax
>
> Having the ability to use numeric constants in hist triggers supports
> a wider range of expressions for creating variables.
I'm not against the patch, but I'm curious to what use case this would be
useful for. In the cover letter it mentions the division and multiplication
for finding associated buckets, but what is the addition / subtraction used
for?
-- Steve
>
> Add support for creating trace event histogram variables from numeric
> literals.
>
> e.g. echo 'hist:keys=common_pid:x=1234,y=size-1024' >> event/trigger
>
> A negative numeric constant is created, using unary minus operator
> (parentheses are required).
>
> e.g. echo 'hist:keys=common_pid:z=-(2)' >> event/trigger
>
> Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
>
next prev parent reply other threads:[~2021-10-19 20:48 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 [this message]
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 ` [PATCH 5/5] tracing/histogram: Document expression arithmetic and constants Kalesh Singh
2021-09-15 20:09 ` [PATCH 0/5] tracing: Extend histogram triggers expression parsing Kalesh Singh
2021-09-30 22:58 ` Namhyung Kim
2021-10-02 0:54 ` Kalesh Singh
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