Messages in this thread Patch in this message | | | Date | Tue, 24 Dec 2019 12:56:53 -0500 | From | "Frank A. Cancio Bello" <> | Subject | [PATCH 1/3] docs: ftrace: Clarify the RAM impact of buffer_size_kb |
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The current text could mislead the user into believing that the number of pages allocated by each CPU ring buffer is calculated by the round up of the division: buffer_size_kb / PAGE_SIZE.
Clarifies that a few extra pages may be allocated to accommodate buffer management meta-data.
Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Suggested-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Frank A. Cancio Bello <frank@generalsoftwareinc.com> --- Documentation/trace/ftrace.rst | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index d2b5657ed33e..5a037bedbf6a 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -185,7 +185,8 @@ of ftrace. Here is a list of some of the key files: CPU buffer and not total size of all buffers. The trace buffers are allocated in pages (blocks of memory that the kernel uses for allocation, usually 4 KB in size). - If the last page allocated has room for more bytes + A few extra pages may be allocated to accommodate buffer management + meta-data. If the last page allocated has room for more bytes than requested, the rest of the page will be used, making the actual allocation bigger than requested or shown. ( Note, the size may not be a multiple of the page size -- 2.17.1
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