rtla: Add --trace-buffer-size option

JIRA: https://issues.redhat.com/browse/RHEL-58061

Conflicts: RHEL-9.x does not have commit fb9e90a ("rtla/timerlat: Make
           user-space threads the default) and that leads to a small merge
           conflict.

commit e9a4062
Author: Daniel Bristot de Oliveira <bristot@kernel.org>
Date:   Thu May 16 16:15:22 2024 +0200

    rtla: Add --trace-buffer-size option

    Add the option allow the users to set a different buffer size for the
    trace. For example, in large systems, the user might be interested on
    reducing the trace buffer to avoid large tracing files.

    The buffer size is specified in kB, and it is only affecting
    the tracing instance.

    The function trace_set_buffer_size() appears on libtracefs v1.6,
    so increase the minimum required version on Makefile.config.

    Link: https://lkml.kernel.org/r/e7c9ca5b3865f28e131a49ec3b984fadf2d056c6.1715860611.git.bristot@kernel.org

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

Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>

Author: lclaudio

Documentation/tools/rtla/common_options.rst

@@ -54,6 +54,9 @@
 
         After starting the workload, let it run for *s* seconds before starting collecting the data, allowing the system to warm-up. Statistical data generated during warm-up is discarded.
 
+**--trace-buffer-size** *kB*
+        Set the per-cpu trace buffer size in kB for the tracing output.
+
 **-h**, **--help**
 
         Print help menu.

tools/tracing/rtla/Makefile

@@ -64,7 +64,7 @@ DOCSRC	=	$(SRCTREE)/../../../Documentation/tools/rtla/
 endif
 
 LIBTRACEEVENT_MIN_VERSION = 1.5
-LIBTRACEFS_MIN_VERSION = 1.3
+LIBTRACEFS_MIN_VERSION = 1.6
 
 .PHONY:	all warnings show_warnings
 all:	warnings rtla

tools/tracing/rtla/src/osnoise_hist.c

@@ -43,6 +43,7 @@ struct osnoise_hist_params {
 	int			bucket_size;
 	int			entries;
 	int			warmup;
+	int			buffer_size;
 };
 
 struct osnoise_hist_cpu {
@@ -484,6 +485,7 @@ static void osnoise_hist_usage(char *usage)
 		"		d:runtime[us|ms|s]:period[us|ms|s] - use SCHED_DEADLINE with runtime and period",
 		"						       in nanoseconds",
 		"	     --warm-up: let the workload run for s seconds before collecting data",
+		"	     --trace-buffer-size kB: set the per-cpu trace buffer size in kB",
 		NULL,
 	};
 
@@ -548,13 +550,14 @@ static struct osnoise_hist_params
 			{"trigger",		required_argument,	0, '4'},
 			{"filter",		required_argument,	0, '5'},
 			{"warm-up",		required_argument,	0, '6'},
+			{"trace-buffer-size",	required_argument,	0, '7'},
 			{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:p:P:r:s:S:t::T:01234:5:6:",
+		c = getopt_long(argc, argv, "a:c:C::b:d:e:E:DhH:p:P:r:s:S:t::T:01234:5:6:7:",
 				 long_options, &option_index);
 
 		/* detect the end of the options. */
@@ -704,6 +707,9 @@ static struct osnoise_hist_params
 		case '6':
 			params->warmup = get_llong_from_str(optarg);
 			break;
+		case '7':
+			params->buffer_size = get_llong_from_str(optarg);
+			break;
 		default:
 			osnoise_hist_usage("Invalid option");
 		}
@@ -910,6 +916,11 @@ int osnoise_hist_main(int argc, char *argv[])
 				goto out_hist;
 		}
 
+		if (params->buffer_size > 0) {
+			retval = trace_set_buffer_size(&record->trace, params->buffer_size);
+			if (retval)
+				goto out_hist;
+		}
 	}
 
 	/*

tools/tracing/rtla/src/osnoise_top.c

@@ -42,6 +42,7 @@ struct osnoise_top_params {
 	int			hk_cpus;
 	int			warmup;
 	int			pretty_output;
+	int			buffer_size;
 	cpu_set_t		hk_cpu_set;
 	struct sched_attr	sched_param;
 	struct trace_events	*events;
@@ -317,6 +318,7 @@ static void osnoise_top_usage(struct osnoise_top_params *params, char *usage)
 		"		d:runtime[us|ms|s]:period[us|ms|s] - use SCHED_DEADLINE with runtime and period",
 		"						       in nanoseconds",
 		"	     --warm-up s: let the workload run for s seconds before collecting data",
+		"	     --trace-buffer-size kB: set the per-cpu trace buffer size in kB",
 		NULL,
 	};
 
@@ -392,13 +394,14 @@ struct osnoise_top_params *osnoise_top_parse_args(int argc, char **argv)
 			{"trigger",		required_argument,	0, '0'},
 			{"filter",		required_argument,	0, '1'},
 			{"warm-up",		required_argument,	0, '2'},
+			{"trace-buffer-size",	required_argument,	0, '3'},
 			{0, 0, 0, 0}
 		};
 
 		/* getopt_long stores the option index here. */
 		int option_index = 0;
 
-		c = getopt_long(argc, argv, "a:c:C::d:De:hH:p:P:qr:s:S:t::T:0:1:2:",
+		c = getopt_long(argc, argv, "a:c:C::d:De:hH:p:P:qr:s:S:t::T:0:1:2:3:",
 				 long_options, &option_index);
 
 		/* Detect the end of the options. */
@@ -529,6 +532,9 @@ struct osnoise_top_params *osnoise_top_parse_args(int argc, char **argv)
 		case '2':
 			params->warmup = get_llong_from_str(optarg);
 			break;
+		case '3':
+			params->buffer_size = get_llong_from_str(optarg);
+			break;
 		default:
 			osnoise_top_usage(params, "Invalid option");
 		}
@@ -740,6 +746,12 @@ int osnoise_top_main(int argc, char **argv)
 			if (retval)
 				goto out_top;
 		}
+
+		if (params->buffer_size > 0) {
+			retval = trace_set_buffer_size(&record->trace, params->buffer_size);
+			if (retval)
+				goto out_top;
+		}
 	}
 
 	/*

tools/tracing/rtla/src/timerlat_hist.c

@@ -53,6 +53,7 @@ struct timerlat_hist_params {
 	int			bucket_size;
 	int			entries;
 	int			warmup;
+	int			buffer_size;
 };
 
 struct timerlat_hist_cpu {
@@ -691,6 +692,7 @@ static void timerlat_hist_usage(char *usage)
 		"	  -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",
+		"	     --trace-buffer-size kB: set the per-cpu trace buffer size in kB",
 		NULL,
 	};
 
@@ -766,13 +768,14 @@ static struct timerlat_hist_params
 			{"no-aa",		no_argument,		0, '9'},
 			{"dump-task",		no_argument,		0, '\1'},
 			{"warm-up",		required_argument,	0, '\2'},
+			{"trace-buffer-size",	required_argument,	0, '\3'},
 			{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\2:",
+		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:\3",
 				 long_options, &option_index);
 
 		/* detect the end of the options. */
@@ -948,6 +951,9 @@ static struct timerlat_hist_params
 		case '\2':
 			params->warmup = get_llong_from_str(optarg);
 			break;
+		case '\3':
+			params->buffer_size = get_llong_from_str(optarg);
+			break;
 		default:
 			timerlat_hist_usage("Invalid option");
 		}
@@ -1182,6 +1188,12 @@ int timerlat_hist_main(int argc, char *argv[])
 			if (retval)
 				goto out_hist;
 		}
+
+		if (params->buffer_size > 0) {
+			retval = trace_set_buffer_size(&record->trace, params->buffer_size);
+			if (retval)
+				goto out_hist;
+		}
 	}
 
 	if (!params->no_aa) {

tools/tracing/rtla/src/timerlat_top.c

@@ -46,6 +46,7 @@ struct timerlat_top_params {
 	int			user_workload;
 	int			pretty_output;
 	int			warmup;
+	int			buffer_size;
 	cpu_set_t		hk_cpu_set;
 	struct sched_attr	sched_param;
 	struct trace_events	*events;
@@ -477,6 +478,7 @@ static void timerlat_top_usage(char *usage)
 		"	  -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",
+		"	     --trace-buffer-size kB: set the per-cpu trace buffer size in kB",
 		NULL,
 	};
 
@@ -544,13 +546,14 @@ static struct timerlat_top_params
 			{"dump-tasks",		no_argument,		0, '4'},
 			{"aa-only",		required_argument,	0, '5'},
 			{"warm-up",		required_argument,	0, '6'},
+			{"trace-buffer-size",	required_argument,	0, '7'},
 			{0, 0, 0, 0}
 		};
 
 		/* 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:np:P:qs:t::T:uU0:1:2:345:6:7:",
 				 long_options, &option_index);
 
 		/* detect the end of the options. */
@@ -714,6 +717,9 @@ static struct timerlat_top_params
 		case '6':
 			params->warmup = get_llong_from_str(optarg);
 			break;
+		case '7':
+			params->buffer_size = get_llong_from_str(optarg);
+			break;
 		default:
 			timerlat_top_usage("Invalid option");
 		}
@@ -952,6 +958,12 @@ int timerlat_top_main(int argc, char *argv[])
 			if (retval)
 				goto out_top;
 		}
+
+		if (params->buffer_size > 0) {
+			retval = trace_set_buffer_size(&record->trace, params->buffer_size);
+			if (retval)
+				goto out_top;
+		}
 	}
 
 	if (!params->no_aa) {

tools/tracing/rtla/src/trace.c

@@ -540,3 +540,18 @@ int trace_is_off(struct trace_instance *tool, struct trace_instance *trace)
 
 	return 0;
 }
+
+/*
+ * trace_set_buffer_size - set the per-cpu tracing buffer size.
+ */
+int trace_set_buffer_size(struct trace_instance *trace, int size)
+{
+	int retval;
+
+	debug_msg("Setting trace buffer size to %d Kb\n", size);
+	retval = tracefs_instance_set_buffer_size(trace->inst, size, -1);
+	if (retval)
+		err_msg("Error setting trace buffer size\n");
+
+	return retval;
+}

tools/tracing/rtla/src/trace.h

@@ -48,3 +48,4 @@ int trace_events_enable(struct trace_instance *instance,
 int trace_event_add_filter(struct trace_events *event, char *filter);
 int trace_event_add_trigger(struct trace_events *event, char *trigger);
 int trace_is_off(struct trace_instance *tool, struct trace_instance *trace);
+int trace_set_buffer_size(struct trace_instance *trace, int size);