From: Tomas Glozar <tglozar@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Jonathan Corbet <corbet@lwn.net>
Cc: linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
John Kacur <jkacur@redhat.com>,
Luis Goncalves <lgoncalv@redhat.com>,
Costa Shulyupin <costa.shul@redhat.com>,
Crystal Wood <crwood@redhat.com>,
Attila Fazekas <afazekas@redhat.com>,
Tomas Glozar <tglozar@redhat.com>
Subject: [PATCH 8/9] Documentation/trace: Specify exact priority for timerlat
Date: Fri, 10 Oct 2025 10:33:37 +0200 [thread overview]
Message-ID: <20251010083338.478961-9-tglozar@redhat.com> (raw)
In-Reply-To: <20251010083338.478961-1-tglozar@redhat.com>
The timerlat tracer documentation mentions that threads are created with
real-time priority, but does not mention which priority and scheduling
class is used.
Add the information so that users do not have to look it up in
trace_osnoise.c.
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---
Documentation/trace/timerlat-tracer.rst | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/Documentation/trace/timerlat-tracer.rst b/Documentation/trace/timerlat-tracer.rst
index 53a56823e903..68d429d454a5 100644
--- a/Documentation/trace/timerlat-tracer.rst
+++ b/Documentation/trace/timerlat-tracer.rst
@@ -43,12 +43,12 @@ It is possible to follow the trace by reading the trace file::
<...>-868 [001] .... 54.030347: #2 context thread timer_latency 4351 ns
-The tracer creates a per-cpu kernel thread with real-time priority that
-prints two lines at every activation. The first is the *timer latency*
-observed at the *hardirq* context before the activation of the thread.
-The second is the *timer latency* observed by the thread. The ACTIVATION
-ID field serves to relate the *irq* execution to its respective *thread*
-execution.
+The tracer creates a per-cpu kernel thread with real-time priority
+SCHED_FIFO:95 that prints two lines at every activation. The first is
+the *timer latency* observed at the *hardirq* context before the activation
+of the thread. The second is the *timer latency* observed by the thread.
+The ACTIVATION ID field serves to relate the *irq* execution to its
+respective *thread* execution.
The *irq*/*thread* splitting is important to clarify in which context
the unexpected high value is coming from. The *irq* context can be
--
2.51.0
next prev parent reply other threads:[~2025-10-10 8:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-10 8:33 [PATCH 0/9] Documentation/rtla: Cover default options Tomas Glozar
2025-10-10 8:33 ` [PATCH 1/9] Documentation/rtla: Fix typo in common_options.txt Tomas Glozar
2025-10-10 8:33 ` [PATCH 2/9] Documentation/rtla: Fix typo in common_timerlat_options.txt Tomas Glozar
2025-10-10 8:33 ` [PATCH 3/9] Documentation/rtla: Fix typo in rtla-timerlat-top.rst Tomas Glozar
2025-10-10 8:33 ` [PATCH 4/9] Documentation/rtla: Fix typo in common_timerlat_options.txt Tomas Glozar
2025-10-10 8:33 ` [PATCH 5/9] Documentation/rtla: Correct tracer name for common options Tomas Glozar
2025-10-10 8:33 ` [PATCH 6/9] Documentation/rtla: Mention default priority Tomas Glozar
2025-10-10 8:33 ` [PATCH 7/9] Documentation/rtla: Mention default cgroup state Tomas Glozar
2025-10-10 8:33 ` Tomas Glozar [this message]
2025-10-10 8:33 ` [PATCH 9/9] Documentation/rtla: Include defaults for tracer options Tomas Glozar
2025-11-03 23:35 ` [PATCH 0/9] Documentation/rtla: Cover default options Jonathan Corbet
2025-11-04 0:22 ` Steven Rostedt
2025-11-05 18:19 ` Jonathan Corbet
2025-11-04 0:32 ` Bagas Sanjaya
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