[v3] ring-buffer/Documentation: Add documentation on buffer_percent file
Commit Message
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
When the buffer_percent file was added to the kernel, the documentation
should have been updated to document what that file does.
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fixes: 03329f9939781 ("tracing: Add tracefs file buffer_percentage")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
Changes since v2: https://lore.kernel.org/linux-trace-kernel/20231226130149.4685c838@gandalf.local.home
- s/watermark/water-mark/ (Randy Dunlap)
- Added '::' and indented the number list so that it has better
formatting (kernel test robot)
Documentation/trace/ftrace.rst | 15 +++++++++++++++
1 file changed, 15 insertions(+)
Comments
On 12/29/23 09:24, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
>
> When the buffer_percent file was added to the kernel, the documentation
> should have been updated to document what that file does.
>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Fixes: 03329f9939781 ("tracing: Add tracefs file buffer_percentage")
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
LGTM. Thanks.
Acked-by: Randy Dunlap <rdunlap@infradead.org>
> ---
> Changes since v2: https://lore.kernel.org/linux-trace-kernel/20231226130149.4685c838@gandalf.local.home
>
> - s/watermark/water-mark/ (Randy Dunlap)
That comment is backwards. :)
No new patch needed IMO.
>
> - Added '::' and indented the number list so that it has better
> formatting (kernel test robot)
>
> Documentation/trace/ftrace.rst | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
> index 933e7efb9f1b..917501a2f348 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 watermark 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
@@ -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 watermark 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