rtla/timerlat_top: Add timerlat user-space support

Add the support for running timerlat threads in user-space. In this
mode, enabled with -u/--user-threads, timerlat dispatches user-space
processes that will loop in the timerlat_fd, measuring the overhead
for going to user-space and then returning to the kernel - in addition
to the existing measurements.

Here is one example of the tool's output with -u enabled:

  $ sudo timerlat top -u -d 600 -q
                                       Timer Latency
    0 00:10:01   |          IRQ Timer Latency (us)        |         Thread Timer Latency (us)      |    Ret user Timer Latency (us)
  CPU COUNT      |      cur       min       avg       max |      cur       min       avg       max |      cur       min       avg       max
    0 #600001    |        0         0         0         3 |        2         1         2         9 |        3         2         3        15
    1 #600001    |        0         0         0         2 |        2         1         2        13 |        2         2         3        18
    2 #600001    |        0         0         0        10 |        2         1         2        16 |        3         2         3        20
    3 #600001    |        0         0         0         7 |        2         1         2        10 |        3         2         3        11
    4 #600000    |        0         0         0        16 |        2         1         2        41 |        3         2         3        58
    5 #600000    |        0         0         0         3 |        2         1         2        10 |        3         2         3        13
    6 #600000    |        0         0         0         5 |        2         1         2         7 |        3         2         3        10
    7 #600000    |        0         0         0         1 |        2         1         2         7 |        3         2         3        10

The tuning setup like -p or -C work for the user-space threads as well.

Link: https://lkml.kernel.org/r/758ad2292a0a1d884138d08219e1a0f572d257a2.1686066600.git.bristot@kernel.org

Cc: William White <chwhite@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/tools/tracing/rtla/src/osnoise.c b/tools/tracing/rtla/src/osnoise.c
index 3ca7a3853943..245e9344932b 100644
--- a/tools/tracing/rtla/src/osnoise.c
+++ b/tools/tracing/rtla/src/osnoise.c
@@ -841,6 +841,67 @@ static void osnoise_put_irq_disable(struct osnoise_context *context)
 	context->orig_opt_irq_disable = OSNOISE_OPTION_INIT_VAL;
 }
 
+static int osnoise_get_workload(struct osnoise_context *context)
+{
+	if (context->opt_workload != OSNOISE_OPTION_INIT_VAL)
+		return context->opt_workload;
+
+	if (context->orig_opt_workload != OSNOISE_OPTION_INIT_VAL)
+		return context->orig_opt_workload;
+
+	context->orig_opt_workload = osnoise_options_get_option("OSNOISE_WORKLOAD");
+
+	return context->orig_opt_workload;
+}
+
+int osnoise_set_workload(struct osnoise_context *context, bool onoff)
+{
+	int opt_workload = osnoise_get_workload(context);
+	int retval;
+
+	if (opt_workload == OSNOISE_OPTION_INIT_VAL)
+		return -1;
+
+	if (opt_workload == onoff)
+		return 0;
+
+	retval = osnoise_options_set_option("OSNOISE_WORKLOAD", onoff);
+	if (retval < 0)
+		return -1;
+
+	context->opt_workload = onoff;
+
+	return 0;
+}
+
+static void osnoise_restore_workload(struct osnoise_context *context)
+{
+	int retval;
+
+	if (context->orig_opt_workload == OSNOISE_OPTION_INIT_VAL)
+		return;
+
+	if (context->orig_opt_workload == context->opt_workload)
+		goto out_done;
+
+	retval = osnoise_options_set_option("OSNOISE_WORKLOAD", context->orig_opt_workload);
+	if (retval < 0)
+		err_msg("Could not restore original OSNOISE_WORKLOAD option\n");
+
+out_done:
+	context->orig_opt_workload = OSNOISE_OPTION_INIT_VAL;
+}
+
+static void osnoise_put_workload(struct osnoise_context *context)
+{
+	osnoise_restore_workload(context);
+
+	if (context->orig_opt_workload == OSNOISE_OPTION_INIT_VAL)
+		return;
+
+	context->orig_opt_workload = OSNOISE_OPTION_INIT_VAL;
+}
+
 /*
  * enable_osnoise - enable osnoise tracer in the trace_instance
  */
@@ -908,6 +969,9 @@ struct osnoise_context *osnoise_context_alloc(void)
 	context->orig_opt_irq_disable	= OSNOISE_OPTION_INIT_VAL;
 	context->opt_irq_disable	= OSNOISE_OPTION_INIT_VAL;
 
+	context->orig_opt_workload	= OSNOISE_OPTION_INIT_VAL;
+	context->opt_workload		= OSNOISE_OPTION_INIT_VAL;
+
 	osnoise_get_context(context);
 
 	return context;
@@ -935,6 +999,7 @@ void osnoise_put_context(struct osnoise_context *context)
 	osnoise_put_print_stack(context);
 	osnoise_put_tracing_thresh(context);
 	osnoise_put_irq_disable(context);
+	osnoise_put_workload(context);
 
 	free(context);
 }