Commit 8b6cbcac authored by Tomas Glozar's avatar Tomas Glozar Committed by Steven Rostedt (Google)
Browse files

rtla/timerlat: Introduce enum timerlat_tracing_mode 

After the introduction of BPF-based sample collection, rtla-timerlat
effectively runs in one of three modes:

- Pure BPF mode, with tracefs only being used to set up the timerlat
tracer. Sample processing and stop on threshold are handled by BPF.

- tracefs mode. BPF is unsupported or kernel is lacking the necessary
trace event (osnoise:timerlat_sample). Stop on theshold is handled by
timerlat tracer stopping tracing in all instances.

- BPF/tracefs mixed mode - BPF is used for sample collection for top or
histogram, tracefs is used for trace output and/or auto-analysis. Stop
on threshold is handled both through BPF program, which stops sample
collection for top/histogram and wakes up rtla, and by timerlat
tracer, which stops tracing for trace output/auto-analysis instances.

Add enum timerlat_tracing_mode, with three values:

- TRACING_MODE_BPF
- TRACING_MODE_TRACEFS
- TRACING_MODE_MIXED

Those represent the modes described above. A field of this type is added
to struct timerlat_params, named "mode", replacing the no_bpf variable.
params->mode is set in timerlat_{top,hist}_parse_args to
TRACING_MODE_BPF or TRACING_MODE_MIXED based on whether trace output
and/or auto-analysis is requested. timerlat_{top,hist}_main then checks
if BPF is not unavailable or disabled, in that case, it sets
params->mode to TRACING_MODE_TRACEFS.

A condition is added to timerlat_apply_config that skips setting
timerlat tracer thresholds if params->mode is TRACING_MODE_BPF (those
are unnecessary, since they only turn off tracing, which is already
turned off in that case, since BPF is used to collect samples).

Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Chang Yin <cyin@redhat.com>
Cc: Costa Shulyupin <costa.shul@redhat.com>
Cc: Crystal Wood <crwood@redhat.com>
Cc: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/20250626123405.1496931-2-tglozar@redhat.com


Signed-off-by: default avatarTomas Glozar <tglozar@redhat.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent d7b8f8e2

tools/tracing/rtla/src/timerlat.c

+15 −9
Original line number Diff line number Diff line
@@ -40,6 +40,11 @@ timerlat_apply_config(struct osnoise_tool *tool, struct timerlat_params *params) 
			CPU_SET(i, &params->monitored_cpus);

	}



	if (params->mode != TRACING_MODE_BPF) {

		/*

		 * In tracefs and mixed mode, timerlat tracer handles stopping

		 * on threshold

		 */

		retval = osnoise_set_stop_us(tool->context, params->stop_us);

		if (retval) {

			err_msg("Failed to set stop us\n");
@@ -51,6 +56,7 @@ timerlat_apply_config(struct osnoise_tool *tool, struct timerlat_params *params) 
			err_msg("Failed to set stop total us\n");

			goto out_err;

		}

	}





	retval = osnoise_set_timerlat_period_us(tool->context,

tools/tracing/rtla/src/timerlat.h

+18 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include "osnoise.h"



/*

 * Define timerlat tracing mode.

 *

 * There are three tracing modes:

 * - tracefs-only, used when BPF is unavailable.

 * - BPF-only, used when BPF is available and neither trace saving nor

 * auto-analysis are enabled.

 * - mixed mode, used when BPF is available and either trace saving or

 * auto-analysis is enabled (which rely on sample collection through

 * tracefs).

 */

enum timerlat_tracing_mode {

	TRACING_MODE_BPF,

	TRACING_MODE_TRACEFS,

	TRACING_MODE_MIXED,

};



struct timerlat_params {

	/* Common params */

	char			*cpus;
@@ -30,6 +47,7 @@ struct timerlat_params { 
	cpu_set_t		hk_cpu_set;

	struct sched_attr	sched_param;

	struct trace_events	*events;

	enum timerlat_tracing_mode mode;

	union {

		struct {

			/* top only */

tools/tracing/rtla/src/timerlat_hist.c

+30 −21
Original line number Diff line number Diff line
@@ -802,6 +802,9 @@ static struct timerlat_params 
	params->bucket_size = 1;

	params->entries = 256;



	/* default to BPF mode */

	params->mode = TRACING_MODE_BPF;



	while (1) {

		static struct option long_options[] = {

			{"auto",		required_argument,	0, 'a'},
@@ -1054,6 +1057,13 @@ static struct timerlat_params 
	if (params->kernel_workload && params->user_workload)

		timerlat_hist_usage("--kernel-threads and --user-threads are mutually exclusive!");



	/*

	 * If auto-analysis or trace output is enabled, switch from BPF mode to

	 * mixed mode

	 */

	if (params->mode == TRACING_MODE_BPF && params->trace_output && !params->no_aa)

		params->mode = TRACING_MODE_MIXED;



	return params;

}
@@ -1149,7 +1159,6 @@ int timerlat_hist_main(int argc, char *argv[]) 
	pthread_t timerlat_u;

	int retval;

	int nr_cpus, i;

	bool no_bpf = false;



	params = timerlat_hist_parse_args(argc, argv);

	if (!params)
@@ -1161,12 +1170,6 @@ int timerlat_hist_main(int argc, char *argv[]) 
		goto out_exit;

	}



	retval = timerlat_hist_apply_config(tool, params);

	if (retval) {

		err_msg("Could not apply config\n");

		goto out_free;

	}



	trace = &tool->trace;

	/*

	 * Save trace instance into global variable so that SIGINT can stop
@@ -1175,22 +1178,28 @@ int timerlat_hist_main(int argc, char *argv[]) 
	 */

	hist_inst = trace;



	/*

	 * Try to enable BPF, unless disabled explicitly.

	 * If BPF enablement fails, fall back to tracefs mode.

	 */

	if (getenv("RTLA_NO_BPF") && strncmp(getenv("RTLA_NO_BPF"), "1", 2) == 0) {

		debug_msg("RTLA_NO_BPF set, disabling BPF\n");

		no_bpf = true;

	}



	if (!no_bpf && !tep_find_event_by_name(trace->tep, "osnoise", "timerlat_sample")) {

		params->mode = TRACING_MODE_TRACEFS;

	} else if (!tep_find_event_by_name(trace->tep, "osnoise", "timerlat_sample")) {

		debug_msg("osnoise:timerlat_sample missing, disabling BPF\n");

		no_bpf = true;

	}



	if (!no_bpf) {

		params->mode = TRACING_MODE_TRACEFS;

	} else {

		retval = timerlat_bpf_init(params);

		if (retval) {

			debug_msg("Could not enable BPF\n");

			no_bpf = true;

			params->mode = TRACING_MODE_TRACEFS;

		}

	}



	retval = timerlat_hist_apply_config(tool, params);

	if (retval) {

		err_msg("Could not apply config\n");

		goto out_free;

	}



	retval = enable_timerlat(trace);
@@ -1320,7 +1329,7 @@ int timerlat_hist_main(int argc, char *argv[]) 
		trace_instance_start(&record->trace);

	if (!params->no_aa)

		trace_instance_start(&aa->trace);

	if (no_bpf) {

	if (params->mode == TRACING_MODE_TRACEFS) {

		trace_instance_start(trace);

	} else {

		retval = timerlat_bpf_attach();
@@ -1333,7 +1342,7 @@ int timerlat_hist_main(int argc, char *argv[]) 
	tool->start_time = time(NULL);

	timerlat_hist_set_signals(params);



	if (no_bpf) {

	if (params->mode == TRACING_MODE_TRACEFS) {

		while (!stop_tracing) {

			sleep(params->sleep_time);
@@ -1362,7 +1371,7 @@ int timerlat_hist_main(int argc, char *argv[]) 
	} else

		timerlat_bpf_wait(-1);



	if (!no_bpf) {

	if (params->mode != TRACING_MODE_TRACEFS) {

		timerlat_bpf_detach();

		retval = timerlat_hist_bpf_pull_data(tool);

		if (retval) {
@@ -1409,10 +1418,10 @@ int timerlat_hist_main(int argc, char *argv[]) 
	osnoise_destroy_tool(aa);

	osnoise_destroy_tool(record);

	osnoise_destroy_tool(tool);

	if (params->mode != TRACING_MODE_TRACEFS)

		timerlat_bpf_destroy();

	free(params);

	free_cpu_idle_disable_states();

	if (!no_bpf)

		timerlat_bpf_destroy();

out_exit:

	exit(return_value);

}

tools/tracing/rtla/src/timerlat_top.c

+34 −23
Original line number Diff line number Diff line
@@ -559,6 +559,9 @@ static struct timerlat_params 
	/* display data in microseconds */

	params->output_divisor = 1000;



	/* default to BPF mode */

	params->mode = TRACING_MODE_BPF;



	while (1) {

		static struct option long_options[] = {

			{"auto",		required_argument,	0, 'a'},
@@ -790,6 +793,13 @@ static struct timerlat_params 
	if (params->kernel_workload && params->user_workload)

		timerlat_top_usage("--kernel-threads and --user-threads are mutually exclusive!");



	/*

	 * If auto-analysis or trace output is enabled, switch from BPF mode to

	 * mixed mode

	 */

	if (params->mode == TRACING_MODE_BPF && params->trace_output && !params->no_aa)

		params->mode = TRACING_MODE_MIXED;



	return params;

}
@@ -994,7 +1004,6 @@ int timerlat_top_main(int argc, char *argv[]) 
	char *max_lat;

	int retval;

	int nr_cpus, i;

	bool no_bpf = false;



	params = timerlat_top_parse_args(argc, argv);

	if (!params)
@@ -1006,12 +1015,6 @@ int timerlat_top_main(int argc, char *argv[]) 
		goto out_exit;

	}



	retval = timerlat_top_apply_config(top, params);

	if (retval) {

		err_msg("Could not apply config\n");

		goto out_free;

	}



	trace = &top->trace;

	/*

	 * Save trace instance into global variable so that SIGINT can stop
@@ -1020,22 +1023,28 @@ int timerlat_top_main(int argc, char *argv[]) 
	 */

	top_inst = trace;



	/*

	 * Try to enable BPF, unless disabled explicitly.

	 * If BPF enablement fails, fall back to tracefs mode.

	 */

	if (getenv("RTLA_NO_BPF") && strncmp(getenv("RTLA_NO_BPF"), "1", 2) == 0) {

		debug_msg("RTLA_NO_BPF set, disabling BPF\n");

		no_bpf = true;

	}



	if (!no_bpf && !tep_find_event_by_name(trace->tep, "osnoise", "timerlat_sample")) {

		params->mode = TRACING_MODE_TRACEFS;

	} else if (!tep_find_event_by_name(trace->tep, "osnoise", "timerlat_sample")) {

		debug_msg("osnoise:timerlat_sample missing, disabling BPF\n");

		no_bpf = true;

	}



	if (!no_bpf) {

		params->mode = TRACING_MODE_TRACEFS;

	} else {

		retval = timerlat_bpf_init(params);

		if (retval) {

			debug_msg("Could not enable BPF\n");

			no_bpf = true;

			params->mode = TRACING_MODE_TRACEFS;

		}

	}



	retval = timerlat_top_apply_config(top, params);

	if (retval) {

		err_msg("Could not apply config\n");

		goto out_free;

	}



	retval = enable_timerlat(trace);
@@ -1166,7 +1175,7 @@ int timerlat_top_main(int argc, char *argv[]) 
		trace_instance_start(&record->trace);

	if (!params->no_aa)

		trace_instance_start(&aa->trace);

	if (no_bpf) {

	if (params->mode == TRACING_MODE_TRACEFS) {

		trace_instance_start(trace);

	} else {

		retval = timerlat_bpf_attach();
@@ -1179,7 +1188,7 @@ int timerlat_top_main(int argc, char *argv[]) 
	top->start_time = time(NULL);

	timerlat_top_set_signals(params);



	if (no_bpf)

	if (params->mode == TRACING_MODE_TRACEFS)

		retval = timerlat_top_main_loop(top, record, params, &params_u);

	else

		retval = timerlat_top_bpf_main_loop(top, record, params, &params_u);
@@ -1187,7 +1196,7 @@ int timerlat_top_main(int argc, char *argv[]) 
	if (retval)

		goto out_top;



	if (!no_bpf)

	if (params->mode != TRACING_MODE_TRACEFS)

		timerlat_bpf_detach();



	if (params->user_workload && !params_u.stopped_running) {
@@ -1239,6 +1248,8 @@ int timerlat_top_main(int argc, char *argv[]) 
		osnoise_destroy_tool(aa);

	osnoise_destroy_tool(record);

	osnoise_destroy_tool(top);

	if (params->mode != TRACING_MODE_TRACEFS)

		timerlat_bpf_destroy();

	free(params);

	free_cpu_idle_disable_states();

out_exit: