Commit 7d0dc957 authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (Google)
Browse files

rtla/timerlat: Add --dma-latency option 

Add the --dma-latency to set /dev/cpu_dma_latency to the
specified value, this aims to avoid having exit from idle
states latencies that could be influencing the analysis.

Link: https://lkml.kernel.org/r/72ddb0d913459f13217086dadafad88a7c46dd28.1646247211.git.bristot@kernel.org



Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 7d38c351

Documentation/tools/rtla/common_timerlat_options.rst

+5 −0
Original line number Diff line number Diff line
@@ -21,3 +21,8 @@ 


        Save the stack trace at the *IRQ* if a *Thread* latency is higher than the

        argument in us.



**--dma-latency** *us*

        Set the /dev/cpu_dma_latency to *us*, aiming to bound exit from idle latencies.

        *cyclictest* sets this value to *0* by default, use **--dma-latency** *0* to have

        similar results.

tools/tracing/rtla/src/timerlat_hist.c

+26 −2
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ struct timerlat_hist_params { 
	int			output_divisor;

	int			duration;

	int			set_sched;

	int			dma_latency;

	struct sched_attr	sched_param;

	struct trace_events	*events;
@@ -432,7 +433,7 @@ 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] \\",

		"	  [-P priority] [-E N] [-b N] [--no-irq] [--no-thread] [--no-header] [--no-summary] \\",

		"	  [--no-index] [--with-zeros]",

		"	  [--no-index] [--with-zeros] [--dma-latency us]",

		"",

		"	  -h/--help: print this menu",

		"	  -a/--auto: set automatic trace mode, stopping the session if argument in us latency is hit",
@@ -456,6 +457,7 @@ static void timerlat_hist_usage(char *usage) 
		"	     --no-summary: do not print summary",

		"	     --no-index: do not print index",

		"	     --with-zeros: print zero only entries",

		"	     --dma-latency us: set /dev/cpu_dma_latency latency <us> to reduce exit from idle latency",

		"	  -P/--priority o:prio|r:prio|f:prio|d:runtime:period : set scheduling parameters",

		"		o:prio - use SCHED_OTHER with prio",

		"		r:prio - use SCHED_RR with prio",
@@ -492,6 +494,9 @@ static struct timerlat_hist_params 
	if (!params)

		exit(1);



	/* disabled by default */

	params->dma_latency = -1;



	/* display data in microseconds */

	params->output_divisor = 1000;

	params->bucket_size = 1;
@@ -522,13 +527,14 @@ static struct timerlat_hist_params 
			{"with-zeros",		no_argument,		0, '5'},

			{"trigger",		required_argument,	0, '6'},

			{"filter",		required_argument,	0, '7'},

			{"dma-latency",		required_argument,	0, '8'},

			{0, 0, 0, 0}

		};



		/* getopt_long stores the option index here. */

		int option_index = 0;



		c = getopt_long(argc, argv, "a:c:b:d:e:E:Dhi:np:P:s:t::T:0123456:7:",

		c = getopt_long(argc, argv, "a:c:b:d:e:E:Dhi:np:P:s:t::T:0123456:7:8:",

				 long_options, &option_index);



		/* detect the end of the options. */
@@ -659,6 +665,13 @@ static struct timerlat_hist_params 
				timerlat_hist_usage("--filter requires a previous -e\n");

			}

			break;

		case '8':

			params->dma_latency = get_llong_from_str(optarg);

			if (params->dma_latency < 0 || params->dma_latency > 10000) {

				err_msg("--dma-latency needs to be >= 0 and < 10000");

				exit(EXIT_FAILURE);

			}

			break;

		default:

			timerlat_hist_usage("Invalid option");

		}
@@ -791,6 +804,7 @@ int timerlat_hist_main(int argc, char *argv[]) 
	struct osnoise_tool *record = NULL;

	struct osnoise_tool *tool = NULL;

	struct trace_instance *trace;

	int dma_latency_fd = -1;

	int return_value = 1;

	int retval;
@@ -826,6 +840,14 @@ int timerlat_hist_main(int argc, char *argv[]) 
		}

	}



	if (params->dma_latency >= 0) {

		dma_latency_fd = set_cpu_dma_latency(params->dma_latency);

		if (dma_latency_fd < 0) {

			err_msg("Could not set /dev/cpu_dma_latency.\n");

			goto out_hist;

		}

	}



	trace_instance_start(trace);



	if (params->trace_output) {
@@ -878,6 +900,8 @@ int timerlat_hist_main(int argc, char *argv[]) 
	}



out_hist:

	if (dma_latency_fd >= 0)

		close(dma_latency_fd);

	trace_events_destroy(&record->trace, params->events);

	params->events = NULL;

	timerlat_free_histogram(tool->data);

tools/tracing/rtla/src/timerlat_top.c

+26 −2
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ struct timerlat_top_params { 
	int			duration;

	int			quiet;

	int			set_sched;

	int			dma_latency;

	struct sched_attr	sched_param;

	struct trace_events	*events;

};
@@ -269,7 +270,7 @@ 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] \\",

		"	  [-P priority]",

		"	  [-P priority] [--dma-latency us]",

		"",

		"	  -h/--help: print this menu",

		"	  -a/--auto: set automatic trace mode, stopping the session if argument in us latency is hit",
@@ -286,6 +287,7 @@ static void timerlat_top_usage(char *usage) 
		"	     --trigger <command>: enable a trace event trigger to the previous -e event",

		"	  -n/--nano: display data in nanoseconds",

		"	  -q/--quiet print only a summary at the end",

		"	     --dma-latency us: set /dev/cpu_dma_latency latency <us> to reduce exit from idle latency",

		"	  -P/--priority o:prio|r:prio|f:prio|d:runtime:period : set scheduling parameters",

		"		o:prio - use SCHED_OTHER with prio",

		"		r:prio - use SCHED_RR with prio",
@@ -322,6 +324,9 @@ static struct timerlat_top_params 
	if (!params)

		exit(1);



	/* disabled by default */

	params->dma_latency = -1;



	/* display data in microseconds */

	params->output_divisor = 1000;
@@ -343,13 +348,14 @@ static struct timerlat_top_params 
			{"trace",		optional_argument,	0, 't'},

			{"trigger",		required_argument,	0, '0'},

			{"filter",		required_argument,	0, '1'},

			{"dma-latency",		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:d:De:hi:np:P:qs:t::T:0:1:",

		c = getopt_long(argc, argv, "a:c:d:De:hi:np:P:qs:t::T:0:1:2:",

				 long_options, &option_index);



		/* detect the end of the options. */
@@ -454,6 +460,13 @@ static struct timerlat_top_params 
				timerlat_top_usage("--filter requires a previous -e\n");

			}

			break;

		case '2': /* dma-latency */

			params->dma_latency = get_llong_from_str(optarg);

			if (params->dma_latency < 0 || params->dma_latency > 10000) {

				err_msg("--dma-latency needs to be >= 0 and < 10000");

				exit(EXIT_FAILURE);

			}

			break;

		default:

			timerlat_top_usage("Invalid option");

		}
@@ -582,6 +595,7 @@ int timerlat_top_main(int argc, char *argv[]) 
	struct osnoise_tool *record = NULL;

	struct osnoise_tool *top = NULL;

	struct trace_instance *trace;

	int dma_latency_fd = -1;

	int return_value = 1;

	int retval;
@@ -617,6 +631,14 @@ int timerlat_top_main(int argc, char *argv[]) 
		}

	}



	if (params->dma_latency >= 0) {

		dma_latency_fd = set_cpu_dma_latency(params->dma_latency);

		if (dma_latency_fd < 0) {

			err_msg("Could not set /dev/cpu_dma_latency.\n");

			goto out_top;

		}

	}



	trace_instance_start(trace);



	if (params->trace_output) {
@@ -673,6 +695,8 @@ int timerlat_top_main(int argc, char *argv[]) 
	}



out_top:

	if (dma_latency_fd >= 0)

		close(dma_latency_fd);

	trace_events_destroy(&record->trace, params->events);

	params->events = NULL;

	timerlat_free_top(top->data);

tools/tracing/rtla/src/utils.c

+33 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <unistd.h>

#include <ctype.h>

#include <errno.h>

#include <fcntl.h>

#include <sched.h>

#include <stdio.h>
@@ -431,3 +432,35 @@ int parse_prio(char *arg, struct sched_attr *sched_param) 
	}

	return 0;

}



/*

 * set_cpu_dma_latency - set the /dev/cpu_dma_latecy

 *

 * This is used to reduce the exit from idle latency. The value

 * will be reset once the file descriptor of /dev/cpu_dma_latecy

 * is closed.

 *

 * Return: the /dev/cpu_dma_latecy file descriptor

 */

int set_cpu_dma_latency(int32_t latency)

{

	int retval;

	int fd;



	fd = open("/dev/cpu_dma_latency", O_RDWR);

	if (fd < 0) {

		err_msg("Error opening /dev/cpu_dma_latency\n");

		return -1;

	}



	retval = write(fd, &latency, 4);

	if (retval < 1) {

		err_msg("Error setting /dev/cpu_dma_latency\n");

		close(fd);

		return -1;

	}



	debug_msg("Set /dev/cpu_dma_latency to %d\n", latency);



	return fd;

}

tools/tracing/rtla/src/utils.h

+1 −0
Original line number Diff line number Diff line
@@ -54,3 +54,4 @@ struct sched_attr { 


int parse_prio(char *arg, struct sched_attr *sched_param);

int set_comm_sched_attr(const char *comm, struct sched_attr *attr);

int set_cpu_dma_latency(int32_t latency);