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Author SHA1 Message Date
Costa Shulyupin 8cbb25db81 tools/rtla: Add fatal() and replace error handling pattern 
The code contains some technical debt in error handling,
which complicates the consolidation of duplicated code.

Introduce an fatal() function to replace the common pattern of
err_msg() followed by exit(EXIT_FAILURE), reducing the length of an
already long function.

Further patches using fatal() follow.

Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
Reviewed-by: Tomas Glozar <tglozar@redhat.com>
Link: https://lore.kernel.org/r/20251011082738.173670-2-costa.shul@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
 2025-11-21 10:30:27 +01:00
Daniel Bristot de Oliveira e8c44d3b71 rtla/timerlat: Do not stop user-space if a cpu is offline 
If no CPU list is passed, timerlat in user-space will dispatch
one thread per sysconf(_SC_NPROCESSORS_CONF). However, not all
CPU might be available, for instance, if HT is disabled.

Currently, rtla timerlat is stopping the session if an user-space
thread cannot set affinity to a CPU, or if a running user-space
thread is killed. However, this is too restrictive.

So, reduce the error to a debug message, and rtla timerlat run as
long as there is at least one user-space thread alive.

Link: https://lore.kernel.org/lkml/59cf2c882900ab7de91c6ee33b382ac7fa6b4ed0.1694781909.git.bristot@kernel.org

Fixes: cdca4f4e5e ("rtla/timerlat_top: Add timerlat user-space support")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
 2023-09-22 14:43:46 +02:00
Daniel Bristot de Oliveira cdca4f4e5e rtla/timerlat_top: Add timerlat user-space support 
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>
 2023-06-13 16:38:51 -04:00