cdca4f4e5e
Add the support for running timerlat threads in user-space. In this
mode, enabled with -u/--user-threads, timerlat dispatches user-space
processes that will loop in the timerlat_fd, measuring the overhead
for going to user-space and then returning to the kernel - in addition
to the existing measurements.
Here is one example of the tool's output with -u enabled:
$ sudo timerlat top -u -d 600 -q
Timer Latency
0 00:10:01 | IRQ Timer Latency (us) | Thread Timer Latency (us) | Ret user Timer Latency (us)
CPU COUNT | cur min avg max | cur min avg max | cur min avg max
0 #600001 | 0 0 0 3 | 2 1 2 9 | 3 2 3 15
1 #600001 | 0 0 0 2 | 2 1 2 13 | 2 2 3 18
2 #600001 | 0 0 0 10 | 2 1 2 16 | 3 2 3 20
3 #600001 | 0 0 0 7 | 2 1 2 10 | 3 2 3 11
4 #600000 | 0 0 0 16 | 2 1 2 41 | 3 2 3 58
5 #600000 | 0 0 0 3 | 2 1 2 10 | 3 2 3 13
6 #600000 | 0 0 0 5 | 2 1 2 7 | 3 2 3 10
7 #600000 | 0 0 0 1 | 2 1 2 7 | 3 2 3 10
The tuning setup like -p or -C work for the user-space threads as well.
Link: https://lkml.kernel.org/r/758ad2292a0a1d884138d08219e1a0f572d257a2.1686066600.git.bristot@kernel.org
Cc: William White <chwhite@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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