Add osnoise/options options

PATCH Superseded Daniel Bristot de Oliveira 3 participants 9 messages Nov 25, 2022 – Nov 30, 2022

Subsystems (3)

Documentation Tracing Tracing OS noise / latency tracers

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lore

Daniel Bristot de Oliveira

author

2022-11-25 21:20 UTC #0 lore raw

v3 cover Add osnoise/options options

Was: Allow osnoise tracer to run without workload [1]

After adding the osnoise/options file, a set of on/off options came to my mind, most based on discussions while debugging problems with Juri and Clark.

The PANIC_ON_STOP option facilitates the vmcore generation to aid in the latency analysis using a crash dump.

The OSNOISE_PREEMPT_DISABLE and OSNOISE_IRQ_DISABLE options refine the type of noise that the osnoise tracer detects, allowing the tool to measure only IRQ-related noise, or NMI/HW-related noise, respectively.

Each patch has a description of the options and the last patch documents them in the osnoise documentation file.

[1] https://lore.kernel.org/r/[email protected]/

Changes from v2:
- rebased on top of linux-trace.git/ftrace/core
- removed the patches already added to the ftrace/core
Changes from v1:
- Changed the cover letter topic
- Add Acked-by Masami to the first patch
- Add the PANIC_ON_STOP option
- Add the OSNOISE_PREEMPT_DISABLE and OSNOISE_IRQ_DISABLE options
- Improved the documentation

Daniel Bristot de Oliveira (3):
tracing/osnoise: Add PANIC_ON_STOP option tracing/osnoise: Add preempt and/or irq disabled options Documentation/osnoise: Add osnoise/options documentation

 Documentation/trace/osnoise-tracer.rst | 20 ++++++++++--
 kernel/trace/trace_osnoise.c           | 44 +++++++++++++++++++++++---
 2 files changed, 57 insertions(+), 7 deletions(-)

Signature · 1 line

2.32.0

Daniel Bristot de Oliveira

author

2022-11-25 21:20 UTC #1 lore raw

PATCH v3 1/3 tracing/osnoise: Add PANIC_ON_STOP option

Often the latency observed in a CPU is not caused by the work being done in the CPU itself, but by work done on another CPU that causes the hardware to stall all CPUs. In this case, it is interesting to know what is happening on ALL CPUs, and the best way to do this is via crash dump analysis.

Add the PANIC_ON_STOP option to osnoise/timerlat tracers. The default behavior is having this option off. When enabled by the user, the system will panic after hitting a stop tracing condition.

This option was motivated by a real scenario that Juri Lelli and I were debugging.

Cc Juri Lelli <[email protected]>

Cc Daniel Bristot de Oliveira <[email protected]>

Cc Steven Rostedt <[email protected]>

Cc Masami Hiramatsu <[email protected]>

Cc Jonathan Corbet <[email protected]>

Signed-off-by Daniel Bristot de Oliveira <[email protected]>

---
 kernel/trace/trace_osnoise.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

kernel/trace/trace_osnoise.c +5 -1

index 3f10dd1f2f1c..801eba0b5cf8 100644
@@ -54,10 +54,11 @@
 enum osnoise_options_index {
 	OSN_DEFAULTS = 0,
 	OSN_WORKLOAD,
+	OSN_PANIC_ON_STOP,
 	OSN_MAX
 };
 
-static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS", "OSNOISE_WORKLOAD" };
+static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS", "OSNOISE_WORKLOAD", "PANIC_ON_STOP" };
 
 #define OSN_DEFAULT_OPTIONS	0x2
 unsigned long osnoise_options	= OSN_DEFAULT_OPTIONS;

@@ -1270,6 +1271,9 @@ static __always_inline void osnoise_stop_tracing(void)
 		trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
 				"stop tracing hit on cpu %d\n", smp_processor_id());
 
+		if (test_bit(OSN_PANIC_ON_STOP, &osnoise_options))
+			panic("tracer hit stop condition on CPU %d\n", smp_processor_id());
+
 		tracer_tracing_off(tr);
 	}
 	rcu_read_unlock();

Signature · 1 line

2.32.0

Daniel Bristot de Oliveira

author

2022-11-25 21:20 UTC #2 lore raw

PATCH v3 2/3 tracing/osnoise: Add preempt/irq disable options

In reply to Daniel Bristot de Oliveira

The osnoise workload runs with preemption and IRQs enabled in such a way as to allow all sorts of noise to disturb osnoise's execution. hwlat tracer has a similar workload but works with irq disabled, allowing only NMIs and the hardware to generate noise.

While thinking about adding an options file to hwlat tracer to allow the system to panic, and other features I was thinking to add, like having a tracepoint at each noise detection, it came to my mind that is easier to make osnoise and also do hardware latency detection than making hwlat "feature compatible" with osnoise.

Other points are:
- osnoise already has an independent cpu file.
- osnoise has a more intuitive interface, e.g., runtime/period vs. window/width (and people often need help remembering what it is).
- osnoise: tracepoints
- osnoise stop options
- osnoise options file itself

Moreover, the user-space side (in rtla) is simplified by reusing the existing osnoise code.

Finally, people have been asking me about using osnoise for hw latency detection, and I have to explain that it was sufficient but not necessary. These options make it sufficient and necessary.

Adding a Suggested-by Clark, as he often asked me about this possibility.

Cc Suggested-by: Clark Williams <[email protected]>

Cc Daniel Bristot de Oliveira <[email protected]>

Cc Steven Rostedt <[email protected]>

Cc Masami Hiramatsu <[email protected]>

Cc Jonathan Corbet <[email protected]>

Signed-off-by Daniel Bristot de Oliveira <[email protected]>

---
 kernel/trace/trace_osnoise.c | 40 +++++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 5 deletions(-)

kernel/trace/trace_osnoise.c +35 -5

index 801eba0b5cf8..14b7f4092982 100644
@@ -55,10 +55,17 @@ enum osnoise_options_index {
 	OSN_DEFAULTS = 0,
 	OSN_WORKLOAD,
 	OSN_PANIC_ON_STOP,
+	OSN_PREEMPT_DISABLE,
+	OSN_IRQ_DISABLE,
 	OSN_MAX
 };
 
-static const char * const osnoise_options_str[OSN_MAX] = { "DEFAULTS", "OSNOISE_WORKLOAD", "PANIC_ON_STOP" };
+static const char * const osnoise_options_str[OSN_MAX] = {
+							"DEFAULTS",
+							"OSNOISE_WORKLOAD",
+							"PANIC_ON_STOP",
+							"OSNOISE_PREEMPT_DISABLE",
+							"OSNOISE_IRQ_DISABLE" };
 
 #define OSN_DEFAULT_OPTIONS	0x2
 unsigned long osnoise_options	= OSN_DEFAULT_OPTIONS;

@@ -1308,6 +1315,8 @@ static void notify_new_max_latency(u64 latency)
  */
 static int run_osnoise(void)
 {
+	bool preempt_disable = test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
+	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
 	struct osnoise_variables *osn_var = this_cpu_osn_var();
 	u64 start, sample, last_sample;
 	u64 last_int_count, int_count;

@@ -1335,6 +1344,14 @@ static int run_osnoise(void)
 	 */
 	threshold = tracing_thresh ? : 5000;
 
+	/*
+	 * IRQ disable also implies in preempt disable.
+	 */
+	if (irq_disable)
+		local_irq_disable();
+	else if (preempt_disable)
+		preempt_disable();
+
 	/*
 	 * Make sure NMIs see sampling first
 	 */

@@ -1422,16 +1439,21 @@ static int run_osnoise(void)
 		 * cond_resched()
 		 */
 		if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
-			local_irq_disable();
+			if (!irq_disable)
+				local_irq_disable();
+
 			rcu_momentary_dyntick_idle();
-			local_irq_enable();
+
+			if (!irq_disable)
+				local_irq_enable();
 		}
 
 		/*
 		 * For the non-preemptive kernel config: let threads runs, if
-		 * they so wish.
+		 * they so wish, unless set not do to so.
 		 */
-		cond_resched();
+		if (!irq_disable && !preempt_disable)
+			cond_resched();
 
 		last_sample = sample;
 		last_int_count = int_count;

@@ -1450,6 +1472,14 @@ static int run_osnoise(void)
 	 */
 	barrier();
 
+	/*
+	 * Return to the preemptive state.
+	 */
+	if (irq_disable)
+		local_irq_enable();
+	else if (preempt_disable)
+		preempt_enable();
+
 	/*
 	 * Save noise info.
 	 */

Signature · 1 line

2.32.0

Steven Rostedt

maintainer

2022-11-28 20:39 UTC #3 lore raw

Re: [PATCH V3 2/3] tracing/osnoise: Add preempt/irq disable options

kernel/trace/trace_osnoise.c static void notify_new_max_latency(u64 latency) · line 1319

Quoted 6 lines · On Fri, 25 Nov 2022 22:20:23 +0100 Daniel Bristot de Oliveira…

kernel/trace/trace_osnoise.c +2 -0

@@ -1308,6 +1315,8 @@ static void notify_new_max_latency(u64 latency)
  */
 static int run_osnoise(void)
 {
+	bool preempt_disable = test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
+	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);

	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
	bool preempt_disable = IS_ENABLED(CONFIG_PREEMPT) &&
			!irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);

kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1351

Quoted 12 lines

kernel/trace/trace_osnoise.c +5 -0

 	struct osnoise_variables *osn_var = this_cpu_osn_var();
 	u64 start, sample, last_sample;
 	u64 last_int_count, int_count;

@@ -1335,6 +1344,14 @@ static int run_osnoise(void)
 	 */
 	threshold = tracing_thresh ? : 5000;
 
+	/*
+	 * IRQ disable also implies in preempt disable.
+	 */
+	if (irq_disable)
+		local_irq_disable();

if (preempt_disable)

Quoted 32 lines

kernel/trace/trace_osnoise.c +11 -4

+		preempt_disable();
+
 	/*
 	 * Make sure NMIs see sampling first
 	 */

@@ -1422,16 +1439,21 @@ static int run_osnoise(void)
 		 * cond_resched()
 		 */
 		if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
-			local_irq_disable();
+			if (!irq_disable)
+				local_irq_disable();
+
 			rcu_momentary_dyntick_idle();
-			local_irq_enable();
+
+			if (!irq_disable)
+				local_irq_enable();
 		}
 
 		/*
 		 * For the non-preemptive kernel config: let threads runs, if
-		 * they so wish.
+		 * they so wish, unless set not do to so.
 		 */
-		cond_resched();
+		if (!irq_disable && !preempt_disable)
+			cond_resched();
 
 		last_sample = sample;
 		last_int_count = int_count;

kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1477

Quoted 6 lines

kernel/trace/trace_osnoise.c +3 -0

@@ -1450,6 +1472,14 @@ static int run_osnoise(void)
 	 */
 	barrier();
 
+	/*
+	 * Return to the preemptive state.
+	 */

if (preempt_disable)

kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1479

Quoted 5 lines

kernel/trace/trace_osnoise.c +4 -0

+		preempt_enable();
+
 
+	if (irq_disable)
+		local_irq_enable();

-- Steve

Quoted 3 lines

kernel/trace/trace_osnoise.c +0 -0
 	/*
 	 * Save noise info.
 	 */

Daniel Bristot de Oliveira

author

2022-11-29 08:27 UTC #4 lore raw

Re: [PATCH V3 2/3] tracing/osnoise: Add preempt/irq disable options

Quoted 13 lines · Steven Rostedt

kernel/trace/trace_osnoise.c static void notify_new_max_latency(u64 latency) · line 1319

Quoted 6 lines · On Fri, 25 Nov 2022 22:20:23 +0100 Daniel Bristot de Oliveira…

kernel/trace/trace_osnoise.c +2 -0

@@ -1308,6 +1315,8 @@ static void notify_new_max_latency(u64 latency)
  */
 static int run_osnoise(void)
 {
+	bool preempt_disable = test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
+	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);

	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
	bool preempt_disable = IS_ENABLED(CONFIG_PREEMPT) &&
			!irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);

Ooops, you are right. I will fix this, and the doc as well, in the v4.

Thanks
-- Daniel

Daniel Bristot de Oliveira

author

2022-11-30 15:47 UTC #5 lore raw

Re: [PATCH V3 2/3] tracing/osnoise: Add preempt/irq disable options

In reply to Steven Rostedt

Quoted 13 lines · Steven Rostedt

kernel/trace/trace_osnoise.c static void notify_new_max_latency(u64 latency) · line 1319

Quoted 6 lines · On Fri, 25 Nov 2022 22:20:23 +0100 Daniel Bristot de Oliveira…

kernel/trace/trace_osnoise.c +2 -0

@@ -1308,6 +1315,8 @@ static void notify_new_max_latency(u64 latency)
  */
 static int run_osnoise(void)
 {
+	bool preempt_disable = test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
+	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);

	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
	bool preempt_disable = IS_ENABLED(CONFIG_PREEMPT) &&
			!irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);

Ooops again, that is not exactly what I wanted, because...

Quoted 34 lines

kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1351

Quoted 12 lines

kernel/trace/trace_osnoise.c +5 -0

 	struct osnoise_variables *osn_var = this_cpu_osn_var();
 	u64 start, sample, last_sample;
 	u64 last_int_count, int_count;

@@ -1335,6 +1344,14 @@ static int run_osnoise(void)
 	 */
 	threshold = tracing_thresh ? : 5000;
 
+	/*
+	 * IRQ disable also implies in preempt disable.
+	 */
+	if (irq_disable)
+		local_irq_disable();

if (preempt_disable)

Quoted 20 lines

kernel/trace/trace_osnoise.c +8 -2

+		preempt_disable();
+
 	/*
 	 * Make sure NMIs see sampling first
 	 */

@@ -1422,16 +1439,21 @@ static int run_osnoise(void)
 		 * cond_resched()
 		 */
 		if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
-			local_irq_disable();
+			if (!irq_disable)
+				local_irq_disable();
+
 			rcu_momentary_dyntick_idle();
-			local_irq_enable();
+
+			if (!irq_disable)
+				local_irq_enable();
 		}

Quoted 5 lines

kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1454
Quoted 5 lines
kernel/trace/trace_osnoise.c +1 -1
 		/*
 		 * For the non-preemptive kernel config: let threads runs, if
-		 * they so wish.
+		 * they so wish, unless set not do to so.
 		 */

Then I end up cond_resched'ing here in the non-preemptive kernel.

Quoted 3 lines

kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1456
Quoted 3 lines
kernel/trace/trace_osnoise.c +2 -1
-		cond_resched();
+		if (!irq_disable && !preempt_disable)
+			cond_resched();

But I also want to avoid this cond_resched if preempt_disable is set.

So, I will merge both things:

	- change the preempt_disable assignment to check !irq_disabled, like:

		/*
		 * Disabling preemption is only required if IRQs are enabled, and the options is set on.
		 */
		preempt_disable = !irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);

	- change the preempt disabled if to
		if (IS_ENABLED(CONFIG_PREEMPT) && preempt_disabled)
			preempt_disable();

I tested with both preemption models (preemptive and not preemptive) and it works fine.

am I missing something?

-- Daniel

Quoted 22 lines

kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1477
Quoted 9 lines
kernel/trace/trace_osnoise.c +3 -0
 		last_sample = sample;
 		last_int_count = int_count;
@@ -1450,6 +1472,14 @@ static int run_osnoise(void)
 	 */
 	barrier();
 
+	/*
+	 * Return to the preemptive state.
+	 */
if (preempt_disable)
kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1479
Quoted 5 lines
kernel/trace/trace_osnoise.c +4 -0
+		preempt_enable();
+
 
+	if (irq_disable)
+		local_irq_enable();
-- Steve
Quoted 3 lines
kernel/trace/trace_osnoise.c +0 -0
 	/*
 	 * Save noise info.
 	 */

Steven Rostedt

maintainer

2022-11-30 16:10 UTC #6 lore raw

Re: [PATCH V3 2/3] tracing/osnoise: Add preempt/irq disable options

Quoted 15 lines · On Wed, 30 Nov 2022 16:47:29 +0100 Daniel Bristot de Oliveira…

Quoted 13 lines · Steven Rostedt
kernel/trace/trace_osnoise.c static void notify_new_max_latency(u64 latency) · line 1319
Quoted 6 lines · On Fri, 25 Nov 2022 22:20:23 +0100 Daniel Bristot de Oliveira…
kernel/trace/trace_osnoise.c +2 -0
@@ -1308,6 +1315,8 @@ static void notify_new_max_latency(u64 latency)
  */
 static int run_osnoise(void)
 {
+	bool preempt_disable = test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);
+	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);  
	bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options);
	bool preempt_disable = IS_ENABLED(CONFIG_PREEMPT) &&
			!irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);  

Quoted 1 line

Ooops again, that is not exactly what I wanted, because...

Then just remove the "IS_ENABLED()" part and it should work just fine.

Quoted 8 lines

kernel/trace/trace_osnoise.c +0 -0

 	struct osnoise_variables *osn_var = this_cpu_osn_var();
 	u64 start, sample, last_sample;
 	u64 last_int_count, int_count;

@@ -1335,6 +1344,14 @@ static int run_osnoise(void)
 	 */
 	threshold = tracing_thresh ? : 5000;

Quoted 8 lines

Quoted 8 lines
kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1351
Quoted 5 lines
kernel/trace/trace_osnoise.c +5 -0
+	/*
+	 * IRQ disable also implies in preempt disable.
+	 */
+	if (irq_disable)
+		local_irq_disable();  
if (preempt_disable)
kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1353
Quoted 1 line
kernel/trace/trace_osnoise.c +1 -0
+		preempt_disable();

The above is a nop when CONFIG_PREEMPT is false.

Quoted 19 lines

kernel/trace/trace_osnoise.c +7 -2

+
 	/*
 	 * Make sure NMIs see sampling first
 	 */

@@ -1422,16 +1439,21 @@ static int run_osnoise(void)
 		 * cond_resched()
 		 */
 		if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
-			local_irq_disable();
+			if (!irq_disable)
+				local_irq_disable();
+
 			rcu_momentary_dyntick_idle();
-			local_irq_enable();
+
+			if (!irq_disable)
+				local_irq_enable();
 		}

Quoted 7 lines

Quoted 5 lines
kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1454
Quoted 5 lines
kernel/trace/trace_osnoise.c +1 -1
 		/*
 		 * For the non-preemptive kernel config: let threads runs, if
-		 * they so wish.
+		 * they so wish, unless set not do to so.
 		 */  
Then I end up cond_resched'ing here in the non-preemptive kernel.

Sorry, I missed the point that you want to *not* cond_resched() even in a CONFIG_PREEMPT is false situation, if preempt_disable flag is set. That's the reason I added the IS_ENABLED(CONFIG_PREEMPT) check at the top. I originally didn't have that, but then thought this should always happen in that case.

Quoted 6 lines

Quoted 4 lines
kernel/trace/trace_osnoise.c static int run_osnoise(void) · line 1456
Quoted 4 lines
kernel/trace/trace_osnoise.c +2 -1
-		cond_resched();
+		if (!irq_disable && !preempt_disable)
+			cond_resched();  
But I also want to avoid this cond_resched if preempt_disable is set.

Right, so just remove the IS_ENABLED() part in the beginning.

Quoted 9 lines

So, I will merge both things:

	- change the preempt_disable assignment to check !irq_disabled, like:

		/*
		 * Disabling preemption is only required if IRQs are enabled, and the options is set on.
		 */
		preempt_disable = !irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options);

Yep (that's what I original had until I changed it)

Quoted 4 lines

	- change the preempt disabled if to
		if (IS_ENABLED(CONFIG_PREEMPT) && preempt_disabled)
			preempt_disable();

No need, preempt_disable() is a nop when CONFIG_PREEMPT is false.

Quoted 4 lines

I tested with both preemption models (preemptive and not preemptive) and it works fine.
am I missing something?

Just that you don't need to add the IS_ENABLED() part at all.

-- Steve

Daniel Bristot de Oliveira

author

2022-11-25 21:20 UTC #7 lore raw

PATCH v3 3/3 Documentation/osnoise: Add osnoise/options documentation

In reply to Daniel Bristot de Oliveira

Add the documentation about the osnoise/options file, the options, and some additional explanation about the OSNOISE_WORKLOAD option.

Cc Daniel Bristot de Oliveira <[email protected]>

Cc Steven Rostedt <[email protected]>

Cc Masami Hiramatsu <[email protected]>

Cc Jonathan Corbet <[email protected]>

Signed-off-by Daniel Bristot de Oliveira <[email protected]>

---
 Documentation/trace/osnoise-tracer.rst | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

Documentation/trace/osnoise-tracer.rst +18 -2

index 3c675ed82b27..0641781b00f5 100644
@@ -92,8 +92,8 @@ Note that the example above shows a high number of HW noise samples.
 The reason being is that this sample was taken on a virtual machine,
 and the host interference is detected as a hardware interference.
 
-Tracer options
----------------------
+Tracer Configuration
+--------------------
 
 The tracer has a set of options inside the osnoise directory, they are:

@@ -115,6 +115,22 @@ The tracer has a set of options inside the osnoise directory, they are:
    NO_OSNOISE_WORKLOAD disables the OSNOISE_WORKLOAD option. The
    special DEAFAULTS option resets all options to the default value.
 
+Tracer Options
+--------------
+
+The osnoise/options file exposes a set of on/off configuration options for
+the osnoise tracer. These options are:
+
+ - DEFAULTS: reset the options to the default value.
+ - OSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
+   section below).
+ - PANIC_ON_STOP: call panic() if the tracer stops. This option serves to
+    capture a vmcore.
+ - OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise
+   workload, allowing only IRQ and hardware-related noise.
+ - OSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,
+   allowing only NMIs and hardware-related noise, like hwlat tracer.
+
 Additional Tracing
 ------------------

Signature · 1 line

2.32.0

Bagas Sanjaya

2022-11-26 12:39 UTC #8 lore raw

Re: [PATCH V3 3/3] Documentation/osnoise: Add osnoise/options documentation

Review

Quoted 11 lines · Daniel Bristot de Oliveira

(quoted diff) +11 -0

+Tracer Options
+--------------
+
+The osnoise/options file exposes a set of on/off configuration options for
+the osnoise tracer. These options are:
+
+ - DEFAULTS: reset the options to the default value.
+ - OSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
+   section below).
+ - PANIC_ON_STOP: call panic() if the tracer stops. This option serves to
+    capture a vmcore.

Excessive indentation makes PANIC_ON_STOP item above become definition list instead. I have to make a small fixup:

---- >8 ----

Documentation/trace/osnoise-tracer.rst +1 -1

index 0641781b00f5e8..f2008e3172231d 100644
@@ -125,7 +125,7 @@ the osnoise tracer. These options are:
  - OSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
    section below).
  - PANIC_ON_STOP: call panic() if the tracer stops. This option serves to
-    capture a vmcore.
+   capture a vmcore.
  - OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise
    workload, allowing only IRQ and hardware-related noise.
  - OSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,

Review

Quoted 5 lines

+ - OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise

(quoted diff) +4 -0

+   workload, allowing only IRQ and hardware-related noise.
+ - OSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,
+   allowing only NMIs and hardware-related noise, like hwlat tracer.
+

Otherwise LGTM.

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An old man doll... just what I always wanted! - Clara