linux-kernel - [RFC v2 1/2] docs: ftrace: Clarify the RAM impact of buffer_size

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2c8f88a60637bef6fa7d58089ff54011c1671b0e.1574655670.git.frank@generalsoftwareinc.com>
Date:   Sun, 24 Nov 2019 23:38:20 -0500
From:   "Frank A. Cancio Bello" <frank@...eralsoftwareinc.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     joel@...lfernandes.org, saiprakash.ranjan@...eaurora.org
Subject: [RFC v2 1/2] 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@...dmis.org>
Suggested-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Signed-off-by: Frank A. Cancio Bello <frank@...eralsoftwareinc.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..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