rtla/timerlat: Make user-space threads the default

After ther -u addition, most of the known users are setting it. And
it makes sense, as it adds more information, and inherits the default
setup for the threads - e.g., cgroups configs.

Thus, if the user-space interface is available, enable -u. Otherwise,
use the in-kernel thread.

Add the -k option to allow the user to request kernel-threads.

Link: https://lkml.kernel.org/r/9241d3089de4091b124f780ed832a0e6646cadaa.1713968967.git.bristot@kernel.org

Cc: Jonathan Corbet <[email protected]>
Cc: Juri Lelli <[email protected]>
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>

Author: Daniel Bristot de Oliveira

Documentation/tools/rtla/common_timerlat_options.rst

@@ -27,12 +27,16 @@
         *cyclictest* sets this value to *0* by default, use **--dma-latency** *0* to have
         similar results.
 
+**-k**, **--kernel-threads**
+
+        Use timerlat kernel-space threads, in contrast of **-u**.
+
 **-u**, **--user-threads**
 
         Set timerlat to run without a workload, and then dispatches user-space workloads
         to wait on the timerlat_fd. Once the workload is awakes, it goes to sleep again
         adding so the measurement for the kernel-to-user and user-to-kernel to the tracer
-        output.
+        output. **--user-threads** will be used unless the user specify **-k**.
 
 **-U**, **--user-load**
 

tools/tracing/rtla/src/timerlat_hist.c

@@ -40,6 +40,7 @@ struct timerlat_hist_params {
 	int			no_aa;
 	int			dump_tasks;
 	int			user_workload;
+	int			kernel_workload;
 	int			user_hist;
 	cpu_set_t		hk_cpu_set;
 	struct sched_attr	sched_param;
@@ -628,7 +629,7 @@ static void timerlat_hist_usage(char *usage)
 		"  usage: [rtla] timerlat hist [-h] [-q] [-d s] [-D] [-n] [-a us] [-p us] [-i us] [-T us] [-s us] \\",
 		"         [-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]",
+		"	  [--no-index] [--with-zeros] [--dma-latency us] [-C[=cgroup_name]] [--no-aa] [--dump-task] [-u|-k]",
 		"	  [--warm-up s]",
 		"",
 		"	  -h/--help: print this menu",
@@ -664,7 +665,8 @@ static void timerlat_hist_usage(char *usage)
 		"		f:prio - use SCHED_FIFO with prio",
 		"		d:runtime[us|ms|s]:period[us|ms|s] - use SCHED_DEADLINE with runtime and period",
 		"						       in nanoseconds",
-		"	  -u/--user-threads: use rtla user-space threads instead of in-kernel timerlat threads",
+		"	  -u/--user-threads: use rtla user-space threads instead of kernel-space timerlat threads",
+		"	  -k/--kernel-threads: use timerlat kernel-space threads instead of rtla user-space 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,
@@ -728,6 +730,7 @@ static struct timerlat_hist_params
 			{"thread",		required_argument,	0, 'T'},
 			{"trace",		optional_argument,	0, 't'},
 			{"user-threads",	no_argument,		0, 'u'},
+			{"kernel-threads",	no_argument,		0, 'k'},
 			{"user-load",		no_argument,		0, 'U'},
 			{"event",		required_argument,	0, 'e'},
 			{"no-irq",		no_argument,		0, '0'},
@@ -748,7 +751,7 @@ static struct timerlat_hist_params
 		/* 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\2:",
+		c = getopt_long(argc, argv, "a:c:C::b:d:e:E:DhH:i:knp:P:s:t::T:uU0123456:7:8:9\1\2:",
 				 long_options, &option_index);
 
 		/* detect the end of the options. */
@@ -831,6 +834,9 @@ static struct timerlat_hist_params
 		case 'i':
 			params->stop_us = get_llong_from_str(optarg);
 			break;
+		case 'k':
+			params->kernel_workload = 1;
+			break;
 		case 'n':
 			params->output_divisor = 1;
 			break;
@@ -942,6 +948,9 @@ static struct timerlat_hist_params
 	if (!params->stop_us && !params->stop_total_us)
 		params->no_aa = 1;
 
+	if (params->kernel_workload && params->user_workload)
+		timerlat_hist_usage("--kernel-threads and --user-threads are mutually exclusive!");
+
 	return params;
 }
 
@@ -1017,6 +1026,22 @@ timerlat_hist_apply_config(struct osnoise_tool *tool, struct timerlat_hist_param
 		auto_house_keeping(&params->monitored_cpus);
 	}
 
+	/*
+	 * If the user did not specify a type of thread, try user-threads first.
+	 * Fall back to kernel threads otherwise.
+	 */
+	if (!params->kernel_workload && !params->user_workload) {
+		retval = tracefs_file_exists(NULL, "osnoise/per_cpu/cpu0/timerlat_fd");
+		if (retval) {
+			debug_msg("User-space interface detected, setting user-threads\n");
+			params->user_workload = 1;
+			params->user_hist = 1;
+		} else {
+			debug_msg("User-space interface not detected, setting kernel-threads\n");
+			params->kernel_workload = 1;
+		}
+	}
+
 	if (params->user_hist) {
 		retval = osnoise_set_workload(tool->context, 0);
 		if (retval) {

tools/tracing/rtla/src/timerlat_top.c

@@ -44,6 +44,7 @@ struct timerlat_top_params {
 	int			hk_cpus;
 	int			user_top;
 	int			user_workload;
+	int			kernel_workload;
 	int			pretty_output;
 	int			warmup;
 	cpu_set_t		hk_cpu_set;
@@ -445,7 +446,7 @@ static void timerlat_top_usage(char *usage)
 		"",
 		"  usage: rtla timerlat [top] [-h] [-q] [-a us] [-d s] [-D] [-n] [-p us] [-i us] [-T us] [-s us] \\",
 		"	  [[-t[=file]] [-e sys[:event]] [--filter <filter>] [--trigger <trigger>] [-c cpu-list] [-H cpu-list]\\",
-		"	  [-P priority] [--dma-latency us] [--aa-only us] [-C[=cgroup_name]] [-u] [--warm-up s]",
+		"	  [-P priority] [--dma-latency us] [--aa-only us] [-C[=cgroup_name]] [-u|-k] [--warm-up s]",
 		"",
 		"	  -h/--help: print this menu",
 		"	  -a/--auto: set automatic trace mode, stopping the session if argument in us latency is hit",
@@ -474,7 +475,8 @@ static void timerlat_top_usage(char *usage)
 		"		f:prio - use SCHED_FIFO with prio",
 		"		d:runtime[us|ms|s]:period[us|ms|s] - use SCHED_DEADLINE with runtime and period",
 		"						       in nanoseconds",
-		"	  -u/--user-threads: use rtla user-space threads instead of in-kernel timerlat threads",
+		"	  -u/--user-threads: use rtla user-space threads instead of kernel-space timerlat threads",
+		"	  -k/--kernel-threads: use timerlat kernel-space threads instead of rtla user-space 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,
@@ -536,6 +538,7 @@ static struct timerlat_top_params
 			{"thread",		required_argument,	0, 'T'},
 			{"trace",		optional_argument,	0, 't'},
 			{"user-threads",	no_argument,		0, 'u'},
+			{"kernel-threads",	no_argument,		0, 'k'},
 			{"user-load",		no_argument,		0, 'U'},
 			{"trigger",		required_argument,	0, '0'},
 			{"filter",		required_argument,	0, '1'},
@@ -550,7 +553,7 @@ static struct timerlat_top_params
 		/* getopt_long stores the option index here. */
 		int option_index = 0;
 
-		c = getopt_long(argc, argv, "a:c:C::d:De:hH:i:np:P:qs:t::T:uU0:1:2:345:6:",
+		c = getopt_long(argc, argv, "a:c:C::d:De:hH:i:knp:P:qs:t::T:uU0:1:2:345:6:",
 				 long_options, &option_index);
 
 		/* detect the end of the options. */
@@ -635,6 +638,9 @@ static struct timerlat_top_params
 		case 'i':
 			params->stop_us = get_llong_from_str(optarg);
 			break;
+		case 'k':
+			params->kernel_workload = true;
+			break;
 		case 'n':
 			params->output_divisor = 1;
 			break;
@@ -729,6 +735,9 @@ static struct timerlat_top_params
 	if (params->no_aa && params->aa_only)
 		timerlat_top_usage("--no-aa and --aa-only are mutually exclusive!");
 
+	if (params->kernel_workload && params->user_workload)
+		timerlat_top_usage("--kernel-threads and --user-threads are mutually exclusive!");
+
 	return params;
 }
 
@@ -807,6 +816,22 @@ timerlat_top_apply_config(struct osnoise_tool *top, struct timerlat_top_params *
 		auto_house_keeping(&params->monitored_cpus);
 	}
 
+	/*
+	 * If the user did not specify a type of thread, try user-threads first.
+	 * Fall back to kernel threads otherwise.
+	 */
+	if (!params->kernel_workload && !params->user_workload) {
+		retval = tracefs_file_exists(NULL, "osnoise/per_cpu/cpu0/timerlat_fd");
+		if (retval) {
+			debug_msg("User-space interface detected, setting user-threads\n");
+			params->user_workload = 1;
+			params->user_top = 1;
+		} else {
+			debug_msg("User-space interface not detected, setting kernel-threads\n");
+			params->kernel_workload = 1;
+		}
+	}
+
 	if (params->user_top) {
 		retval = osnoise_set_workload(top->context, 0);
 		if (retval) {