[PATCH V8 1/9] tracing/osnoise: Do not follow tracing_cpumask

From: Daniel Bristot de Oliveira
Date: Fri Oct 29 2021 - 15:01:02 EST


In preparation to support multiple instances, decouple the
osnoise/timelat workload from instance-specific tracing_cpumask.

Different instances can have conflicting cpumasks, making osnoise
workload management needlessly complex. Osnoise already has its
global cpumask.

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@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Tom Zanussi <zanussi@xxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Clark Williams <williams@xxxxxxxxxx>
Cc: John Kacur <jkacur@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: linux-rt-users@xxxxxxxxxxxxxxx
Cc: linux-trace-devel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
---
kernel/trace/trace_osnoise.c | 24 ++++++------------------
1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index ce053619f289..73f9609cba3d 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -1553,13 +1553,9 @@ 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 osnoise is allowed to 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 +1576,8 @@ 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 +1589,6 @@ 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 +1691,10 @@ 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,
--
2.31.1