linux-kernel - Re: ftrace performance impact with different configuration

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <CAH+eYFDb4r235jAGjr7j5R5C+9YK9WeXXjVZGWQUB=330sOi0Q@mail.gmail.com>
Date:	Thu, 29 Dec 2011 21:12:28 +0530
From:	Rabin Vincent <rabin@....in>
To:	Lei Wen <adrian.wenl@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	leiwen@...vell.com
Subject: Re: ftrace performance impact with different configuration

On Thu, Dec 29, 2011 at 14:08, Lei Wen <adrian.wenl@...il.com> wrote:
> 2. Seem dynamic ftrace also could involve some penalty for the running
> system, although it patching the running kernel with nop stub...
>
> For the second item, is there anyone done some research before that
> could zero the cost for the running system when the tracing is not
> enabled yet?

One thing that needs to be fixed (for ARM) is that for the new-style
mcounts, the nop that's currently being done is not really a nop -- it
removes the function call, but there is still an unnecessary push/pop
sequence.  This should be modified to have the push {lr} removed too.
(Two instructions replaced instead of one.)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/