Re: [PATCH V4 01/19] trace/osnoise: Do not follow tracing_cpumask

Daniel Bristot de Oliveira
2021-10-25T07:49:55Z

On 10/23/21 04:23, Steven Rostedt wrote:
> On Thu, 21 Oct 2021 14:56:39 +0200
> Daniel Bristot de Oliveira <bristot@kernel.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@goodmis.org>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Tom Zanussi <zanussi@kernel.org>
>> Cc: Masami Hiramatsu <mhiramat@kernel.org>
>> Cc: Juri Lelli <juri.lelli@redhat.com>
>> Cc: Clark Williams <williams@redhat.com>
>> Cc: John Kacur <jkacur@redhat.com>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>> Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
>> Cc: linux-rt-users@vger.kernel.org
>> Cc: linux-trace-devel@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.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,
>