linux-kernel - Re: [PATCH 1/2] locking: Add lock contention tracepoints

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Message-ID: <20220317120753.4cd73f9e@gandalf.local.home>
Date:   Thu, 17 Mar 2022 12:07:53 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Byungchul Park <byungchul.park@....com>,
        paulmck <paulmck@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Radoslaw Burny <rburny@...gle.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH 1/2] locking: Add lock contention tracepoints

On Thu, 17 Mar 2022 09:32:55 -0400 (EDT)
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> Unless there is a particular reason for using preprocessor defines here, the
> following form is typically better because it does not pollute the preprocessor
> defines, e.g.:
> 
> enum lock_contention_flags {
>         LCB_F_SPIN =   1U << 0;
>         LCB_F_READ =   1U << 1;
>         LCB_F_WRITE =  1U << 2;
>         LCB_F_RT =     1U << 3;
>         LCB_F_PERCPU = 1U << 4;
> };

If you do this, then to use the __print_flags(), You'll also need to add:

TRACE_DEFINE_ENUM(LCB_F_SPIN);
TRACE_DEFINE_ENUM(LCB_F_READ);
TRACE_DEFINE_ENUM(LCB_F_WRITE);
TRACE_DEFINE_ENUM(LCB_F_RT);
TRACE_DEFINE_ENUM(LCB_F_PERCPU);

Which does slow down boot up slightly.

-- Steve