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| author | Frank A. Cancio Bello <frank@generalsoftwareinc.com> | 2019-12-25 03:06:05 +0300 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2020-01-10 20:51:34 +0300 |
| commit | a65d634e63644d05a22f32e5f2e56dde4f7ee77b (patch) | |
| tree | c5fa0a12b5e2845a74dab7d3727d4624a6116d41 /Documentation/trace | |
| parent | 6f7f8ef713a24ccea341a7f0cb92ef2b6b297f01 (diff) | |
| download | linux-a65d634e63644d05a22f32e5f2e56dde4f7ee77b.tar.xz | |
docs: ftrace: Clarify the RAM impact of buffer_size_kb
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>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frank A. Cancio Bello <frank@generalsoftwareinc.com>
Link: https://lore.kernel.org/r/6f33be5f3d60e5ffc061d8d2b329d3d3ccf22a8c.1577231751.git.frank@generalsoftwareinc.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 46df39300d22..8575aed7b74b 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -187,7 +187,8 @@ 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 |