1RTLA-HWNOISE(1) RTLA-HWNOISE(1)
2
6 rtla-hwnoise - Detect and quantify hardware-related noise
7
9 rtla hwnoise [OPTIONS]
10
12 rtla hwnoise collects the periodic summary from the osnoise tracer run‐
13 ning with interrupts disabled. By disabling interrupts, and the sched‐
14 uling of threads as a consequence, only non-maskable interrupts and
15 hardware-related noise is allowed.
16 The tool also allows the configurations of the osnoise tracer and the
18 collection of the tracer output.
19
21 -a, --auto us
22 Set the automatic trace mode. This mode sets some commonly used op‐
23 tions while debugging the system. It is equivalent to use -s us -T 1
24 -t.
25 -p, --period us
27 Set the osnoise tracer period in microseconds.
28 -r, --runtime us
30 Set the osnoise tracer runtime in microseconds.
31 -s, --stop us
33 Stop the trace if a single sample is higher than the argument in mi‐
34 croseconds. If -T is set, it will also save the trace to the out‐
35 put.
36 -S, --stop-total us
38 Stop the trace if the total sample is higher than the argument in
39 microseconds. If -T is set, it will also save the trace to the out‐
40 put.
41 -T, --threshold us
43 Specify the minimum delta between two time reads to be considered
44 noise. The default threshold is 5 us.
45 -q, --quiet
47 Print only a summary at the end of the session.
48 -c, --cpus cpu-list
50 Set the osnoise tracer to run the sample threads in the cpu-list.
51 -H, --house-keeping cpu-list
53 Run rtla control threads only on the given cpu-list.
54 -d, --duration time[s|m|h|d]
56 Set the duration of the session.
57 -D, --debug
59 Print debug info.
60 -t, --trace[=file]
62 Save the stopped trace to [file|osnoise_trace.txt].
63 -e, --event sys:event
65 Enable an event in the trace (-t) session. The argument can be a
66 specific event, e.g., -e sched:sched_switch, or all events of a sys‐
67 tem group, e.g., -e sched. Multiple -e are allowed. It is only ac‐
68 tive when -t or -a are set.
69 --filter <filter>
71 Filter the previous -e sys:event event with <filter>. For further
72 information about event filtering see
73 https://www.kernel.org/doc/html/latest/trace/events.html#event-filtering.
74 --trigger <trigger>
76 Enable a trace event trigger to the previous -e sys:event. If
77 the hist: trigger is activated, the output histogram will be au‐
78 tomatically saved to a file named system_event_hist.txt. For
79 example, the command:
80 rtla <command> <mode> -t -e osnoise:irq_noise --trig‐
82 ger="hist:key=desc,duration/1000:sort=desc,dura‐
83 tion/1000:vals=hitcount"
84 Will automatically save the content of the histogram associated
86 to osnoise:irq_noise event in osnoise_irq_noise_hist.txt.
87 For further information about event trigger see
89 https://www.kernel.org/doc/html/latest/trace/events.html#event-triggers.
90 -P, --priority o:prio|r:prio|f:prio|d:runtime:period
92 Set scheduling parameters to the osnoise tracer threads, the format
93 to set the priority are:
94 • o:prio - use SCHED_OTHER with prio;
96 • r:prio - use SCHED_RR with prio;
98 • f:prio - use SCHED_FIFO with prio;
100 • d:runtime[us|ms|s]:period[us|ms|s] - use SCHED_DEADLINE with run‐
102 time and period in nanoseconds.
103 -C, --cgroup[=cgroup]
105 Set a cgroup to the tracer's threads. If the -C option is passed
106 without arguments, the tracer's thread will inherit rtla's cgroup.
107 Otherwise, the threads will be placed on the cgroup passed to the
108 option.
109 -h, --help
111 Print help menu.
112
114 In the example below, the rtla hwnoise tool is set to run on CPUs 1-7
115 on a system with 8 cores/16 threads with hyper-threading enabled.
116 The tool is set to detect any noise higher than one microsecond, to run
118 for ten minutes, displaying a summary of the report at the end of the
119 session:
120 # rtla hwnoise -c 1-7 -T 1 -d 10m -q
122 Hardware-related Noise
123 duration: 0 00:10:00 | time is in us
124 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
125 1 #599 599000000 138 99.99997 3 3 4 74
126 2 #599 599000000 85 99.99998 3 3 4 75
127 3 #599 599000000 86 99.99998 4 3 6 75
128 4 #599 599000000 81 99.99998 4 4 2 75
129 5 #599 599000000 85 99.99998 2 2 2 75
130 6 #599 599000000 76 99.99998 2 2 0 75
131 7 #599 599000000 77 99.99998 3 3 0 75
132 The first column shows the CPU, and the second column shows how many
134 Periods the tool ran during the session. The Runtime is the time the
135 tool effectively runs on the CPU. The Noise column is the sum of all
136 noise that the tool observed, and the % CPU Aval is the relation be‐
137 tween the Runtime and Noise.
138 The Max Noise column is the maximum hardware noise the tool detected in
140 a single period, and the Max Single is the maximum single noise seen.
141 The HW and NMI columns show the total number of hardware and NMI noise
143 occurrence observed by the tool.
144 For example, CPU 3 ran 599 periods of 1 second Runtime. The CPU re‐
146 ceived 86 us of noise during the entire execution, leaving 99.99997 %
147 of CPU time for the application. In the worst single period, the CPU
148 caused 4 us of noise to the application, but it was certainly caused by
149 more than one single noise, as the Max Single noise was of 3 us. The
150 CPU has HW noise, at a rate of six occurrences/ten minutes. The CPU
151 also has NMIs, at a higher frequency: around seven per second.
152 The tool should report 0 hardware-related noise in the ideal situation.
154 For example, by disabling hyper-threading to remove the hardware noise,
155 and disabling the TSC watchdog to remove the NMI (it is possible to
156 identify this using tracing options of rtla hwnoise), it was possible
157 to reach the ideal situation in the same hardware:
158 # rtla hwnoise -c 1-7 -T 1 -d 10m -q
160 Hardware-related Noise
161 duration: 0 00:10:00 | time is in us
162 CPU Period Runtime Noise % CPU Aval Max Noise Max Single HW NMI
163 1 #599 599000000 0 100.00000 0 0 0 0
164 2 #599 599000000 0 100.00000 0 0 0 0
165 3 #599 599000000 0 100.00000 0 0 0 0
166 4 #599 599000000 0 100.00000 0 0 0 0
167 5 #599 599000000 0 100.00000 0 0 0 0
168 6 #599 599000000 0 100.00000 0 0 0 0
169 7 #599 599000000 0 100.00000 0 0 0 0
170
172 rtla-osnoise(1)
173 Osnoise tracer documentation: <‐
175 https://www.kernel.org/doc/html/latest/trace/osnoise-tracer.html>
176
178 Written by Daniel Bristot de Oliveira <bristot@kernel.org>
179
181 Report bugs to <linux-kernel@vger.kernel.org> and <‐
182 linux-trace-devel@vger.kernel.org>
183
185 rtla is Free Software licensed under the GNU GPLv2
186
188 Copyright (C) 2021 Red Hat, Inc. Free use of this software is granted
189 under the terms of the GNU Public License (GPL).
190 RTLA-HWNOISE(1)