rtla: Add the --warm-up option

On many cases, the results right after the startup are different
from the rest of the execution, biasing the results. For example,
on osnoise, the scheduler might take some time to adapt to the new
busy-loop workload.

Add the --warm-up <seconds> option, adding a warm-up phase (in
seconds) where the workload is set, but the results are discarded.

Link: https://lkml.kernel.org/r/e682d5ce5af90f123bd13220f63d5c3d118a92be.1713968967.git.bristot@kernel.org

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>

1 files changed, 32 insertions, 17 deletions

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index b12c6b571dd4..da1c353bdac9 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -52,6 +52,7 @@ struct timerlat_hist_params {
 	char			with_zeros;
 	int			bucket_size;
 	int			entries;
+	int			warmup;
 };
 
 struct timerlat_hist_cpu {
@@ -628,6 +629,7 @@ static void timerlat_hist_usage(char *usage)
 		"         [-t[=file]] [-e sys[:event]] [--filter <filter>] [--trigger <trigger>] [-c cpu-list] [-H cpu-list]\\",
 		"	  [-P priority] [-E N] [-b N] [--no-irq] [--no-thread] [--no-header] [--no-summary] \\",
 		"	  [--no-index] [--with-zeros] [--dma-latency us] [-C[=cgroup_name]] [--no-aa] [--dump-task] [-u]",
+		"	  [--warm-up s]",
 		"",
 		"	  -h/--help: print this menu",
 		"	  -a/--auto: set automatic trace mode, stopping the session if argument in us latency is hit",
@@ -664,6 +666,7 @@ static void timerlat_hist_usage(char *usage)
 		"						       in nanoseconds",
 		"	  -u/--user-threads: use rtla user-space threads instead of in-kernel timerlat threads",
 		"	  -U/--user-load: enable timerlat for user-defined user-space workload",
+		"	     --warm-up s: let the workload run for s seconds before collecting data",
 		NULL,
 	};
 
@@ -738,13 +741,14 @@ static struct timerlat_hist_params
 			{"dma-latency",		required_argument,	0, '8'},
 			{"no-aa",		no_argument,		0, '9'},
 			{"dump-task",		no_argument,		0, '\1'},
+			{"warm-up",		required_argument,	0, '\2'},
 			{0, 0, 0, 0}
 		};
 
 		/* getopt_long stores the option index here. */
 		int option_index = 0;
 
-		c = getopt_long(argc, argv, "a:c:C::b:d:e:E:DhH:i:np:P:s:t::T:uU0123456:7:8:9\1",
+		c = getopt_long(argc, argv, "a:c:C::b:d:e:E:DhH:i:np:P:s:t::T:uU0123456:7:8:9\1\2:",
 				 long_options, &option_index);
 
 		/* detect the end of the options. */
@@ -913,6 +917,9 @@ static struct timerlat_hist_params
 		case '\1':
 			params->dump_tasks = 1;
 			break;
+		case '\2':
+			params->warmup = get_llong_from_str(optarg);
+			break;
 		default:
 			timerlat_hist_usage("Invalid option");
 		}
@@ -1167,22 +1174,6 @@ int timerlat_hist_main(int argc, char *argv[])
 		}
 	}
 
-	/*
-	 * Start the tracers here, after having set all instances.
-	 *
-	 * Let the trace instance start first for the case of hitting a stop
-	 * tracing while enabling other instances. The trace instance is the
-	 * one with most valuable information.
-	 */
-	if (params->trace_output)
-		trace_instance_start(&record->trace);
-	if (!params->no_aa)
-		trace_instance_start(&aa->trace);
-	trace_instance_start(trace);
-
-	tool->start_time = time(NULL);
-	timerlat_hist_set_signals(params);
-
 	if (params->user_workload) {
 		/* rtla asked to stop */
 		params_u.should_run = 1;
@@ -1202,6 +1193,29 @@ int timerlat_hist_main(int argc, char *argv[])
 			err_msg("Error creating timerlat user-space threads\n");
 	}
 
+	if (params->warmup > 0) {
+		debug_msg("Warming up for %d seconds\n", params->warmup);
+		sleep(params->warmup);
+		if (stop_tracing)
+			goto out_hist;
+	}
+
+	/*
+	 * Start the tracers here, after having set all instances.
+	 *
+	 * Let the trace instance start first for the case of hitting a stop
+	 * tracing while enabling other instances. The trace instance is the
+	 * one with most valuable information.
+	 */
+	if (params->trace_output)
+		trace_instance_start(&record->trace);
+	if (!params->no_aa)
+		trace_instance_start(&aa->trace);
+	trace_instance_start(trace);
+
+	tool->start_time = time(NULL);
+	timerlat_hist_set_signals(params);
+
 	while (!stop_tracing) {
 		sleep(params->sleep_time);
 
@@ -1227,6 +1241,7 @@ int timerlat_hist_main(int argc, char *argv[])
 			}
 		}
 	}
+
 	if (params->user_workload && !params_u.stopped_running) {
 		params_u.should_run = 0;
 		sleep(1);