Commit a23c05fd authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira
Browse files

tools/rtla: Add -U/--user-load option to timerlat 

The timerlat tracer provides an interface for any application to wait
for the timerlat's periodic wakeup. Currently, rtla timerlat uses it
to dispatch its user-space workload (-u option).

But as the tracer interface is generic, rtla timerlat can also be used
to monitor any workload that uses it. For example, a user might
place their own workload to wait on the tracer interface, and
monitor the results with rtla timerlat.

Add the -U option to rtla timerlat top and hist. With this option, rtla
timerlat will not dispatch its workload but only setting up the
system, waiting for a user to dispatch its workload.

The sample code in this patch is an example of python application
that loops in the timerlat tracer fd.

To use it, dispatch:

 # rtla timerlat -U

In a terminal, then run the python program on another terminal,
specifying the CPU to run it. For example, setting on CPU 1:

 #./timerlat_load.py 1

Then rtla timerlat will start printing the statistics of the
./timerlat_load.py app.

An interesting point is that the "Ret user Timer Latency" value
is the overall response time of the load. The sample load does
a memory copy to exemplify that.

The stop tracing options on rtla timerlat works in this setup
as well, including auto analysis.

Link: https://lkml.kernel.org/r/36e6bcf18fe15c7601048fd4c65aeb193c502cc8.1707229706.git.bristot@kernel.org



Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@kernel.org>
parent 012e4e77

Documentation/tools/rtla/common_timerlat_options.rst

+6 −0
Original line number Diff line number Diff line
@@ -33,3 +33,9 @@ 
        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.



**-U**, **--user-load**



        Set timerlat to run without workload, waiting for the user to dispatch a per-cpu

        task that waits for a new period on the tracing/osnoise/per_cpu/cpu$ID/timerlat_fd.

        See linux/tools/rtla/sample/timerlat_load.py for an example of user-load code.

tools/tracing/rtla/sample/timerlat_load.py

0 → 100644
+74 −0
Original line number Diff line number Diff line 
#!/usr/bin/env python3

# SPDX-License-Identifier: GPL-2.0-only

#

# Copyright (C) 2024 Red Hat, Inc. Daniel Bristot de Oliveira <bristot@kernel.org>

#

# This is a sample code about how to use timerlat's timer by any workload

# so rtla can measure and provide auto-analysis for the overall latency (IOW

# the response time) for a task.

#

# Before running it, you need to dispatch timerlat with -U option in a terminal.

# Then # run this script pinned to a CPU on another terminal. For example:

#

# timerlat_load.py 1 -p 95

#

# The "Timerlat IRQ" is the IRQ latency, The thread latency is the latency

# for the python process to get the CPU. The Ret from user Timer Latency is

# the overall latency. In other words, it is the response time for that

# activation.

#

# This is just an example, the load is reading 20MB of data from /dev/full

# It is in python because it is easy to read :-)



import argparse

import sys

import os



parser = argparse.ArgumentParser(description='user-space timerlat thread in Python')

parser.add_argument("cpu", help='CPU to run timerlat thread')

parser.add_argument("-p", "--prio", help='FIFO priority')



args = parser.parse_args()



try:

    affinity_mask = { int(args.cpu) }

except:

    print("Invalid cpu: " + args.cpu)

    exit(1)



try:

    os.sched_setaffinity(0, affinity_mask);

except:

    print("Error setting affinity")

    exit(1)



if (args.prio):

    try:

        param = os.sched_param(int(args.prio))

        os.sched_setscheduler(0, os.SCHED_FIFO, param)

    except:

        print("Error setting priority")

        exit(1)



try:

    timerlat_path = "/sys/kernel/tracing/osnoise/per_cpu/cpu" + args.cpu + "/timerlat_fd"

    timerlat_fd = open(timerlat_path, 'r')

except:

    print("Error opening timerlat fd, did you run timerlat -U?")

    exit(1)



try:

    data_fd = open("/dev/full", 'r');

except:

    print("Error opening data fd")



while True:

    try:

        timerlat_fd.read(1)

        data_fd.read(20*1024*1024)

    except:

        print("Leaving")

        break



timerlat_fd.close()

data_fd.close()

tools/tracing/rtla/src/timerlat_hist.c

+11 −5
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ struct timerlat_hist_params { 
	int			hk_cpus;

	int			no_aa;

	int			dump_tasks;

	int			user_workload;

	int			user_hist;

	cpu_set_t		hk_cpu_set;

	struct sched_attr	sched_param;
@@ -534,6 +535,7 @@ static void timerlat_hist_usage(char *usage) 
		"		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-load: enable timerlat for user-defined user-space workload",

		NULL,

	};
@@ -595,6 +597,7 @@ static struct timerlat_hist_params 
			{"thread",		required_argument,	0, 'T'},

			{"trace",		optional_argument,	0, 't'},

			{"user-threads",	no_argument,		0, 'u'},

			{"user-load",		no_argument,		0, 'U'},

			{"event",		required_argument,	0, 'e'},

			{"no-irq",		no_argument,		0, '0'},

			{"no-thread",		no_argument,		0, '1'},
@@ -613,7 +616,7 @@ 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:u0123456:7:8:9\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",

				 long_options, &option_index);



		/* detect the end of the options. */
@@ -724,6 +727,9 @@ static struct timerlat_hist_params 
				params->trace_output = "timerlat_trace.txt";

			break;

		case 'u':

			params->user_workload = 1;

			/* fallback: -u implies in -U */

		case 'U':

			params->user_hist = 1;

			break;

		case '0': /* no irq */
@@ -985,7 +991,7 @@ int timerlat_hist_main(int argc, char *argv[]) 
		}

	}



	if (params->cgroup && !params->user_hist) {

	if (params->cgroup && !params->user_workload) {

		retval = set_comm_cgroup("timerlat/", params->cgroup_name);

		if (!retval) {

			err_msg("Failed to move threads to cgroup\n");
@@ -1049,7 +1055,7 @@ int timerlat_hist_main(int argc, char *argv[]) 
	tool->start_time = time(NULL);

	timerlat_hist_set_signals(params);



	if (params->user_hist) {

	if (params->user_workload) {

		/* rtla asked to stop */

		params_u.should_run = 1;

		/* all threads left */
@@ -1086,14 +1092,14 @@ int timerlat_hist_main(int argc, char *argv[]) 
			break;



		/* is there still any user-threads ? */

		if (params->user_hist) {

		if (params->user_workload) {

			if (params_u.stopped_running) {

				debug_msg("timerlat user-space threads stopped!\n");

				break;

			}

		}

	}

	if (params->user_hist && !params_u.stopped_running) {

	if (params->user_workload && !params_u.stopped_running) {

		params_u.should_run = 0;

		sleep(1);

	}

tools/tracing/rtla/src/timerlat_top.c

+10 −4
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ struct timerlat_top_params { 
	int			cgroup;

	int			hk_cpus;

	int			user_top;

	int			user_workload;

	cpu_set_t		hk_cpu_set;

	struct sched_attr	sched_param;

	struct trace_events	*events;
@@ -364,6 +365,7 @@ static void timerlat_top_usage(char *usage) 
		"		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-load: enable timerlat for user-defined user-space workload",

		NULL,

	};
@@ -423,6 +425,7 @@ static struct timerlat_top_params 
			{"thread",		required_argument,	0, 'T'},

			{"trace",		optional_argument,	0, 't'},

			{"user-threads",	no_argument,		0, 'u'},

			{"user-load",		no_argument,		0, 'U'},

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

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

			{"dma-latency",		required_argument,	0, '2'},
@@ -435,7 +438,7 @@ 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:u0:1:2:345:",

		c = getopt_long(argc, argv, "a:c:C::d:De:hH:i:np:P:qs:t::T:uU0:1:2:345:",

				 long_options, &option_index);



		/* detect the end of the options. */
@@ -552,6 +555,9 @@ static struct timerlat_top_params 


			break;

		case 'u':

			params->user_workload = true;

			/* fallback: -u implies -U */

		case 'U':

			params->user_top = true;

			break;

		case '0': /* trigger */
@@ -869,7 +875,7 @@ int timerlat_top_main(int argc, char *argv[]) 
	top->start_time = time(NULL);

	timerlat_top_set_signals(params);



	if (params->user_top) {

	if (params->user_workload) {

		/* rtla asked to stop */

		params_u.should_run = 1;

		/* all threads left */
@@ -912,7 +918,7 @@ int timerlat_top_main(int argc, char *argv[]) 
			break;



		/* is there still any user-threads ? */

		if (params->user_top) {

		if (params->user_workload) {

			if (params_u.stopped_running) {

				debug_msg("timerlat user space threads stopped!\n");

				break;
@@ -920,7 +926,7 @@ int timerlat_top_main(int argc, char *argv[]) 
		}

	}



	if (params->user_top && !params_u.stopped_running) {

	if (params->user_workload && !params_u.stopped_running) {

		params_u.should_run = 0;

		sleep(1);

	}