linux-kernel - Re: [RFC PATCH V2 9/9] tracing: Add timerlat tracer

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Date:   Fri, 14 May 2021 10:55:53 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Kate Carcia <kcarcia@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Clark Willaims <williams@...hat.com>,
        John Kacur <jkacur@...hat.com>, linux-doc@...r.kernel.org
Subject: Re: [RFC PATCH V2 9/9] tracing: Add timerlat tracer

Hi Daniel,

Just a couple of things I noticed while playing with this nice additon.

On 23/04/21 23:05, Daniel Bristot de Oliveira wrote:

...

> +/**
> + * tlat_var_reset - Reset the values of the given timerlat_variables
> + */
> +static inline void tlat_var_reset(void)
> +{
> +	struct timerlat_variables *tlat_var;
> +	int cpu;
>  	/*
>  	 * So far, all the values are initialized as 0, so
>  	 * zeroing the structure is perfect.
>  	 */
> -	memset(osn_var, 0, sizeof(struct osnoise_variables));
> +	for_each_cpu(cpu, cpu_online_mask) {
> +		memset(tlat_var, 0, sizeof(struct timerlat_variables));
> +		tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu);

Think these two above want to be the other way around?

> +	}
>  }

...

> +#ifdef CONFIG_TIMERLAT_TRACER
> +static void timerlat_tracer_start(struct trace_array *tr)
> +{
> +	int retval;
> +
> +	if (osnoise_busy)
> +		return;
> +
> +	retval = __osnoise_tracer_start(tr);
> +	if (retval)
> +		goto out_err;
> +
> +	osnoise_data.timerlat_tracer = 1;

It seems this needs to be set before calling __osnoise_tracer_start()?

Thanks!

Juri