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

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Message-ID: <154ce81c-0a65-1639-740d-a506fd8cdaef@redhat.com>
Date:   Fri, 14 May 2021 10:59:41 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     Juri Lelli <juri.lelli@...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

On 5/14/21 10:55 AM, Juri Lelli wrote:
> 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?

Arrrggg! :-) you are right...

>> +	}
>>  }
> 
> ...
> 
>> +#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()?

Yep, my bad! two last minute cleanups that broke things...

I will change these two things in the v3.

Thanks!
-- Daniel

> Thanks!
> 
> Juri
>