[PATCH 0/3] rtla/timerlat: Set OSNOISE_WORKLOAD for kernel threads

[PATCH 0/3] rtla/timerlat: Set OSNOISE_WORKLOAD for kernel threads

[Tomas Glozar]

The patchset makes both rtla-timerlat-hist and rtla-timerlat-top set
OSNOISE_WORKLOAD to the proper value ("on" when running with -k, "off"
when running with -u) every time the option is available instead of setting it
only when running with -u.

This prevents rtla timerlat -k from giving no results when
NO_OSNOISE_WORKLOAD is set, either manually or by an abnormally exited earlier
run of rtla timerlat -u.

osnoise_set_workload is made to distinguish between the option missing
altogether and it failing to be set. In the first case, rtla-timerlat will
ignore setting the option to preserve compatibility of kernel-thread mode
on older kernels without the OSNOISE_WORKLOAD option.

Tomas Glozar (3):
  rtla/osnoise: Distinguish missing workload option
  rtla/timerlat_hist: Set OSNOISE_WORKLOAD for kernel threads
  rtla/timerlat_top: Set OSNOISE_WORKLOAD for kernel threads

 tools/tracing/rtla/src/osnoise.c       |  2 +-
 tools/tracing/rtla/src/timerlat_hist.c | 15 +++++++++------
 tools/tracing/rtla/src/timerlat_top.c  | 15 +++++++++------
 3 files changed, 19 insertions(+), 13 deletions(-)

-- 
2.47.1

[PATCH 1/3] rtla/osnoise: Distinguish missing workload option

[Tomas Glozar]

osnoise_set_workload returns -1 for both missing OSNOISE_WORKLOAD option
and failure in setting the option.

Return -1 for missing and -2 for failure to distinguish them.

Cc: stable@vger.kernel.org
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---
 tools/tracing/rtla/src/osnoise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/tracing/rtla/src/osnoise.c b/tools/tracing/rtla/src/osnoise.c
index 245e9344932b..699a83f538a8 100644
--- a/tools/tracing/rtla/src/osnoise.c
+++ b/tools/tracing/rtla/src/osnoise.c
@@ -867,7 +867,7 @@ int osnoise_set_workload(struct osnoise_context *context, bool onoff)
 
 	retval = osnoise_options_set_option("OSNOISE_WORKLOAD", onoff);
 	if (retval < 0)
-		return -1;
+		return -2;
 
 	context->opt_workload = onoff;
 
-- 
2.47.1

[PATCH 2/3] rtla/timerlat_hist: Set OSNOISE_WORKLOAD for kernel threads

[Tomas Glozar]

When using rtla timerlat with userspace threads (-u or -U), rtla
disables the OSNOISE_WORKLOAD option in
/sys/kernel/tracing/osnoise/options. This option is not re-enabled in a
subsequent run with kernel-space threads, leading to rtla collecting no
results if the previous run exited abnormally:

$ rtla timerlat hist -u
^\Quit (core dumped)
$ rtla timerlat hist -k -d 1s
Index
over:
count:
min:
avg:
max:
ALL:        IRQ       Thr       Usr
count:        0         0         0
min:          -         -         -
avg:          -         -         -
max:          -         -         -

The issue persists until OSNOISE_WORKLOAD is set manually by running:
$ echo OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options

Set OSNOISE_WORKLOAD when running rtla with kernel-space threads if
available to fix the issue.

Cc: stable@vger.kernel.org
Fixes: ed774f7481fa ("rtla/timerlat_hist: Add timerlat user-space support")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---
 tools/tracing/rtla/src/timerlat_hist.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 4403cc4eba30..66dbc034bdc7 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -1100,12 +1100,15 @@ timerlat_hist_apply_config(struct osnoise_tool *tool, struct timerlat_hist_param
 		}
 	}
 
-	if (params->user_hist) {
-		retval = osnoise_set_workload(tool->context, 0);
-		if (retval) {
-			err_msg("Failed to set OSNOISE_WORKLOAD option\n");
-			goto out_err;
-		}
+	/*
+	* Set workload according to type of thread if the kernel supports it.
+	* On kernels without support, user threads will have already failed
+	* on missing timerlat_fd, and kernel threads do not need it.
+	*/
+	retval = osnoise_set_workload(tool->context, params->kernel_workload);
+	if (retval < -1) {
+		err_msg("Failed to set OSNOISE_WORKLOAD option\n");
+		goto out_err;
 	}
 
 	return 0;
-- 
2.47.1

[PATCH 3/3] rtla/timerlat_top: Set OSNOISE_WORKLOAD for kernel threads

[Tomas Glozar]

Apply fix from previous commit also to timerlat-top.

Cc: stable@vger.kernel.org
Fixes: cdca4f4e5e8e ("rtla/timerlat_top: Add timerlat user-space support")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---
 tools/tracing/rtla/src/timerlat_top.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index 059b468981e4..521f9822e747 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -851,12 +851,15 @@ timerlat_top_apply_config(struct osnoise_tool *top, struct timerlat_top_params *
 		}
 	}
 
-	if (params->user_top) {
-		retval = osnoise_set_workload(top->context, 0);
-		if (retval) {
-			err_msg("Failed to set OSNOISE_WORKLOAD option\n");
-			goto out_err;
-		}
+	/*
+	* Set workload according to type of thread if the kernel supports it.
+	* On kernels without support, user threads will have already failed
+	* on missing timerlat_fd, and kernel threads do not need it.
+	*/
+	retval = osnoise_set_workload(top->context, params->kernel_workload);
+	if (retval < -1) {
+		err_msg("Failed to set OSNOISE_WORKLOAD option\n");
+		goto out_err;
 	}
 
 	if (isatty(STDOUT_FILENO) && !params->quiet)
-- 
2.47.1

Re: [PATCH 0/3] rtla/timerlat: Set OSNOISE_WORKLOAD for kernel threads

[Steven Rostedt]

On Tue,  7 Jan 2025 15:48:20 +0100
Tomas Glozar <tglozar@redhat.com> wrote:

> The patchset makes both rtla-timerlat-hist and rtla-timerlat-top set
> OSNOISE_WORKLOAD to the proper value ("on" when running with -k, "off"
> when running with -u) every time the option is available instead of setting it
> only when running with -u.
> 
> This prevents rtla timerlat -k from giving no results when
> NO_OSNOISE_WORKLOAD is set, either manually or by an abnormally exited earlier
> run of rtla timerlat -u.
> 
> osnoise_set_workload is made to distinguish between the option missing
> altogether and it failing to be set. In the first case, rtla-timerlat will
> ignore setting the option to preserve compatibility of kernel-thread mode
> on older kernels without the OSNOISE_WORKLOAD option.
> 
> Tomas Glozar (3):
>   rtla/osnoise: Distinguish missing workload option
>   rtla/timerlat_hist: Set OSNOISE_WORKLOAD for kernel threads
>   rtla/timerlat_top: Set OSNOISE_WORKLOAD for kernel threads
> 
>  tools/tracing/rtla/src/osnoise.c       |  2 +-
>  tools/tracing/rtla/src/timerlat_hist.c | 15 +++++++++------
>  tools/tracing/rtla/src/timerlat_top.c  | 15 +++++++++------
>  3 files changed, 19 insertions(+), 13 deletions(-)
> 

BTW, are you going to be implementing any selftests for rtla so that it is
easy to test these changes and check for regressions?

-- Steve

Re: [PATCH 0/3] rtla/timerlat: Set OSNOISE_WORKLOAD for kernel threads

[Tomas Glozar]

út 7. 1. 2025 v 22:43 odesílatel Steven Rostedt <rostedt@goodmis.org> napsal:
>
> BTW, are you going to be implementing any selftests for rtla so that it is
> easy to test these changes and check for regressions?

Ah right, I promised that some time ago. I have a simple test suite
adapted from CKI tests [1] that is close to being ready, I was having
some doubts about the implementation, but I will send it after adding
a few comments into the code so it can be discussed.

I have discovered already through the tests that this OSNOISE_WORKLOAD
issue also affects rtla-osnoise, not only rtla-timerlat, so it is
definitely at least somehow useful.

[1] - https://gitlab.com/redhat/centos-stream/tests/kernel/kernel-tests/-/blob/main/rt-tests/us/rtla/

> -- Steve
>

Tomas