[RFC v2 1/2] docs: ftrace: Clarify the RAM impact of buffer_size_kb

[Frank A. Cancio Bello]

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@xxxxxxxxxxx>
Suggested-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Frank A. Cancio Bello <frank@xxxxxxxxxxxxxxxxxxxxxx>
---
 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..2b21068ebf8e 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