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

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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: Daniel Bristot de Oliveira <bristot@kernel.org>
This commit is contained in:
Daniel Bristot de Oliveira 2024-02-06 15:32:06 +01:00
parent 012e4e77df
commit a23c05fd76
4 changed files with 101 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/tools/rtla/common_timerlat_options.rst
View File

@ -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.

74
tools/tracing/rtla/sample/timerlat_load.py Normal file
View File

@ -0,0 +1,74 @@
#!/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()

16
tools/tracing/rtla/src/timerlat_hist.c
View File

@ -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);
}

14
tools/tracing/rtla/src/timerlat_top.c
View File

@ -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);
}