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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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ring-buffer/Documentation: Add documentation on buffer_percent file

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>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231229122402.537eb252@gandalf.local.home

authored by

Steven Rostedt (Google) and committed by
Jonathan Corbet 4b2df884 d78bcf64

+15
+15
Documentation/trace/ftrace.rst
··· 180 180 Only active when the file contains a number greater than 0. 181 181 (in microseconds) 182 182 183 + buffer_percent: 184 + 185 + This is the watermark for how much the ring buffer needs to be filled 186 + before a waiter is woken up. That is, if an application calls a 187 + blocking read syscall on one of the per_cpu trace_pipe_raw files, it 188 + will block until the given amount of data specified by buffer_percent 189 + is in the ring buffer before it wakes the reader up. This also 190 + controls how the splice system calls are blocked on this file:: 191 + 192 + 0 - means to wake up as soon as there is any data in the ring buffer. 193 + 50 - means to wake up when roughly half of the ring buffer sub-buffers 194 + are full. 195 + 100 - means to block until the ring buffer is totally full and is 196 + about to start overwriting the older data. 197 + 183 198 buffer_size_kb: 184 199 185 200 This sets or displays the number of kilobytes each CPU