From patchwork Tue Dec 26 18:01:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13504922 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1818353E10; Tue, 26 Dec 2023 18:01:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFD22C433C7; Tue, 26 Dec 2023 18:01:05 +0000 (UTC) Date: Tue, 26 Dec 2023 13:01:49 -0500 From: Steven Rostedt To: LKML , linux-doc@vger.kernel.org, Linux Trace Kernel , Jonathan Corbet Cc: Masami Hiramatsu , Mathieu Desnoyers Subject: [PATCH v2] ring-buffer/Documentation: Add documentation on buffer_percent file Message-ID: <20231226130149.4685c838@gandalf.local.home> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" When the buffer_percent file was added to the kernel, the documentation should have been updated to document what that file does. Fixes: 03329f9939781 ("tracing: Add tracefs file buffer_percentage") Signed-off-by: Steven Rostedt (Google) --- Changes since v1: https://lore.kernel.org/all/20231226123525.71a6d0fb@gandalf.local.home/ - Fixed some grammar issues. Documentation/trace/ftrace.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 933e7efb9f1b..84b810a6cf76 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -180,6 +180,21 @@ of ftrace. Here is a list of some of the key files: Only active when the file contains a number greater than 0. (in microseconds) + buffer_percent: + + This is the water-mark for how much the ring buffer needs to be filled + before a waiter is woken up. That is, if an application calls a + blocking read syscall on one of the per_cpu trace_pipe_raw files, it + will block until the given amount of data specified by buffer_percent + is in the ring buffer before it wakes the reader up. This also + controls how the splice system calls are blocked on this file. + + 0 - means to wake up as soon as there is any data in the ring buffer. + 50 - means to wake up when roughly half of the ring buffer sub-buffers + are full. + 100 - means to block until the ring buffer is totally full and is + about to start overwriting the older data. + buffer_size_kb: This sets or displays the number of kilobytes each CPU