[for-next][PATCH 06/11] tracing/osnoise: Add OSNOISE_WORKLOAD option

Steven Rostedt
2022-11-24T14:51:28Z

From: Daniel Bristot de Oliveira <bristot@kernel.org>

The osnoise tracer is not only a tracer, and a set of tracepoints,
but also a workload dispatcher.

In preparation for having other workloads, e.g., in user-space,
add an option to avoid dispatching the workload.

By not dispatching the workload, the osnoise: tracepoints become
generic events to measure the execution time of *any* task on Linux.

For example:

# cd /sys/kernel/tracing/
# cat osnoise/options
DEFAULTS OSNOISE_WORKLOAD
# echo NO_OSNOISE_WORKLOAD > osnoise/options
# cat osnoise/options
NO_DEFAULTS NO_OSNOISE_WORKLOAD
# echo osnoise > set_event
# echo osnoise > current_tracer
# tail -8 trace
make-94722 [002] d..3. 1371.794507: thread_noise: make:94722 start 1371.794302286 duration 200897 ns
sh-121042 [020] d..3. 1371.794534: thread_noise: sh:121042 start 1371.781610976 duration 8943683 ns
make-121097 [005] d..3. 1371.794542: thread_noise: make:121097 start 1371.794481522 duration 60444 ns
<...>-40 [005] d..3. 1371.794550: thread_noise: migration/5:40 start 1371.794542256 duration 7154 ns
<idle>-0 [018] dNh2. 1371.794554: irq_noise: reschedule:253 start 1371.794553547 duration 40 ns
<idle>-0 [018] dNh2. 1371.794561: irq_noise: local_timer:236 start 1371.794556222 duration 4890 ns
<idle>-0 [018] .Ns2. 1371.794563: softirq_noise: SCHED:7 start 1371.794561803 duration 992 ns
<idle>-0 [018] d..3. 1371.794566: thread_noise: swapper/18:0 start 1371.781368110 duration 13191798 ns

In preparation for the rtla exec_time tracer/tool and
rtla osnoise --user option.

Link: https://lkml.kernel.org/r/f5cfbd37aefd419eefe9243b4d2fc38ed5753fe4.1668692096.git.bristot@kernel.org

Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace_osnoise.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 17b77fe3950b..3f10dd1f2f1c 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -53,12 +53,13 @@
*/
enum osnoise_options_index {
OSN_DEFAULTS = 0,
+ OSN_WORKLOAD,
OSN_MAX
};

-static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS" };
+static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS", "OSNOISE_WORKLOAD" };

-#define OSN_DEFAULT_OPTIONS 0
+#define OSN_DEFAULT_OPTIONS 0x2
unsigned long osnoise_options = OSN_DEFAULT_OPTIONS;

/*
@@ -1186,11 +1187,12 @@ trace_sched_switch_callback(void *data, bool preempt,
unsigned int prev_state)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
+ int workload = test_bit(OSN_WORKLOAD, &osnoise_options);

- if (p->pid != osn_var->pid)
+ if ((p->pid != osn_var->pid) || !workload)
thread_exit(osn_var, p);

- if (n->pid != osn_var->pid)
+ if ((n->pid != osn_var->pid) || !workload)
thread_entry(osn_var, n);
}

@@ -1723,9 +1725,16 @@ static void stop_kthread(unsigned int cpu)
struct task_struct *kthread;

kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
- if (kthread)
+ if (kthread) {
kthread_stop(kthread);
- per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+ per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+ } else {
+ if (!test_bit(OSN_WORKLOAD, &osnoise_options)) {
+ per_cpu(per_cpu_osnoise_var, cpu).sampling = false;
+ barrier();
+ return;
+ }
+ }
}

/*
@@ -1759,6 +1768,13 @@ static int start_kthread(unsigned int cpu)
snprintf(comm, 24, "timerlat/%d", cpu);
main = timerlat_main;
} else {
+ /* if no workload, just return */
+ if (!test_bit(OSN_WORKLOAD, &osnoise_options)) {
+ per_cpu(per_cpu_osnoise_var, cpu).sampling = true;
+ barrier();
+ return 0;
+ }
+
snprintf(comm, 24, "osnoise/%d", cpu);
}

--
2.35.1