linux-kernel - Re: [PATCH V4 01/19] trace/osnoise: Do not follow tracing

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Date:   Mon, 25 Oct 2021 09:26:18 +0200
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Tom Zanussi <zanussi@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        John Kacur <jkacur@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-rt-users@...r.kernel.org, linux-trace-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 01/19] trace/osnoise: Do not follow tracing_cpumask

On 10/23/21 04:23, Steven Rostedt wrote:
> On Thu, 21 Oct 2021 14:56:39 +0200
> Daniel Bristot de Oliveira <bristot@...nel.org> wrote:
> 
>> In preparation to support multiple instances, decople the
> 
>     "decouple"
> 
>> osnoise/timelat workload from instance specific tracing_cpumask.
>>
>> Different instances can have conflicing cpumasks, making osnoise
> 
>    "conflicting"
> 
> May I suggest a spell check for your commit logs? ;-)



Ooops, I will fix them. I use Grammarly on most of my texts, but sometimes I
forget to re-check.

>> workload management needlessly complex. Osnoise already have its
>> global cpu mask.
>>
>> I also thought about using the first instance mask, but the
>> "first" instance could be removed before the others.
>>
>> This also fixes the problem that changing the tracing_mask was not
>> re-starting the trace.
>>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Tom Zanussi <zanussi@...nel.org>
>> Cc: Masami Hiramatsu <mhiramat@...nel.org>
>> Cc: Juri Lelli <juri.lelli@...hat.com>
>> Cc: Clark Williams <williams@...hat.com>
>> Cc: John Kacur <jkacur@...hat.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
>> Cc: Daniel Bristot de Oliveira <bristot@...nel.org>
>> Cc: linux-rt-users@...r.kernel.org
>> Cc: linux-trace-devel@...r.kernel.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Daniel Bristot de Oliveira <bristot@...nel.org>
>> ---
>>  kernel/trace/trace_osnoise.c | 25 +++++++------------------
>>  1 file changed, 7 insertions(+), 18 deletions(-)
>>
>> diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
>> index ce053619f289..7b1f8187764c 100644
>> --- a/kernel/trace/trace_osnoise.c
>> +++ b/kernel/trace/trace_osnoise.c
>> @@ -1553,13 +1553,10 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
>>  
>>  	cpus_read_lock();
>>  	/*
>> -	 * Run only on CPUs in which trace and osnoise are allowed to run.
>> +	 * Run only on online CPUs in which trace and osnoise are allowed to
> 
>   which trace and osnise? I thought we were removing "trace"?


You are correct, I will remove the trace from the comment.

Thanks!
-- Daniel

> -- Steve
> 
>> +	 * run.
>>  	 */
>> -	cpumask_and(current_mask, tr->tracing_cpumask, &osnoise_cpumask);
>> -	/*
>> -	 * And the CPU is online.
>> -	 */
>> -	cpumask_and(current_mask, cpu_online_mask, current_mask);
>> +	cpumask_and(current_mask, cpu_online_mask, &osnoise_cpumask);
>>  
>>  	for_each_possible_cpu(cpu)
>>  		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
>> @@ -1580,10 +1577,8 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
>>  #ifdef CONFIG_HOTPLUG_CPU
>>  static void osnoise_hotplug_workfn(struct work_struct *dummy)
>>  {
>> -	struct trace_array *tr = osnoise_trace;
>>  	unsigned int cpu = smp_processor_id();
>>  
>> -
>>  	mutex_lock(&trace_types_lock);
>>  
>>  	if (!osnoise_busy)
>> @@ -1595,9 +1590,6 @@ static void osnoise_hotplug_workfn(struct work_struct *dummy)
>>  	if (!cpumask_test_cpu(cpu, &osnoise_cpumask))
>>  		goto out_unlock;
>>  
>> -	if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))
>> -		goto out_unlock;
>> -
>>  	start_kthread(cpu);
>>  
>>  out_unlock:
>> @@ -1700,13 +1692,10 @@ static void osnoise_tracer_stop(struct trace_array *tr);
>>   * interface to the osnoise trace. By default, it lists all  CPUs,
>>   * in this way, allowing osnoise threads to run on any online CPU
>>   * of the system. It serves to restrict the execution of osnoise to the
>> - * set of CPUs writing via this interface. Note that osnoise also
>> - * respects the "tracing_cpumask." Hence, osnoise threads will run only
>> - * on the set of CPUs allowed here AND on "tracing_cpumask." Why not
>> - * have just "tracing_cpumask?" Because the user might be interested
>> - * in tracing what is running on other CPUs. For instance, one might
>> - * run osnoise in one HT CPU while observing what is running on the
>> - * sibling HT CPU.
>> + * set of CPUs writing via this interface. Why not use "tracing_cpumask"?
>> + * Because the user might be interested in tracing what is running on
>> + * other CPUs. For instance, one might run osnoise in one HT CPU
>> + * while observing what is running on the sibling HT CPU.
>>   */
>>  static ssize_t
>>  osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
>