linux-kernel - [PATCH 4/4] Documentation/rtla: Include BPF sample collection

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Message-ID: <20250311114936.148012-5-tglozar@redhat.com>
Date: Tue, 11 Mar 2025 12:49:36 +0100
From: Tomas Glozar <tglozar@...hat.com>
To: Steven Rostedt <rostedt@...dmis.org>,
	Jonathan Corbet <corbet@....net>
Cc: linux-trace-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	John Kacur <jkacur@...hat.com>,
	Luis Goncalves <lgoncalv@...hat.com>,
	Tomas Glozar <tglozar@...hat.com>
Subject: [PATCH 4/4] Documentation/rtla: Include BPF sample collection

Add dependencies needed to build rtla with BPF sample collection support
to README, and document both ways of sample collection in the manpages.

Signed-off-by: Tomas Glozar <tglozar@...hat.com>
---
 Documentation/tools/rtla/common_timerlat_description.rst | 8 ++++++++
 tools/tracing/rtla/README.txt                            | 7 +++++++
 2 files changed, 15 insertions(+)

diff --git a/Documentation/tools/rtla/common_timerlat_description.rst b/Documentation/tools/rtla/common_timerlat_description.rst
index 8cd3e717baa8..49fcae3ffdec 100644
--- a/Documentation/tools/rtla/common_timerlat_description.rst
+++ b/Documentation/tools/rtla/common_timerlat_description.rst
@@ -8,3 +8,11 @@ The *timerlat* tracer outputs information in two ways. It periodically
 prints the timer latency at the timer *IRQ* handler and the *Thread*
 handler. It also enables the trace of the most relevant information via
 **osnoise:** tracepoints.
+
+The **rtla timerlat** tool sets the options of the *timerlat* tracer
+and collects and displays a summary of the results. By default,
+the collection is done synchronously in kernel space using a dedicated
+BPF program attached to the *timerlat* tracer. If either BPF or
+the **osnoise:timerlat_sample** tracepoint it attaches to is
+unavailable, the **rtla timerlat** tool falls back to using tracefs to
+process the data asynchronously in user space.
diff --git a/tools/tracing/rtla/README.txt b/tools/tracing/rtla/README.txt
index dd5621038c55..43e98311d10f 100644
--- a/tools/tracing/rtla/README.txt
+++ b/tools/tracing/rtla/README.txt
@@ -13,6 +13,13 @@ RTLA depends on the following libraries and tools:
  - libtraceevent
  - libcpupower (optional, for --deepest-idle-state)
 
+For BPF sample collection support, the following extra dependencies are
+required:
+
+ - libbpf 1.0.0 or later
+ - bpftool with skeleton support
+ - clang with BPF CO-RE support
+
 It also depends on python3-docutils to compile man pages.
 
 For development, we suggest the following steps for compiling rtla:
-- 
2.48.1