public inbox for linux-kernel@vger.kernel.org
 help / color / mirror / Atom feed
From: "Philippe Rétornaz" <philippe.retornaz@epfl.ch>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-arm-kernel@lists.infradead.org,
	Rabin Vincent <rabin@rab.in>,
	leiwen@marvell.com, Lei Wen <adrian.wenl@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: ftrace performance impact with different configuration
Date: Sat, 31 Dec 2011 00:31:55 +0100	[thread overview]
Message-ID: <2631878.q7bjHk7YBM@laptop> (raw)
In-Reply-To: <1325283941.24045.15.camel@gandalf.stny.rr.com>

Le vendredi 30 décembre 2011 17:25:41 Steven Rostedt a écrit :
> On Fri, 2011-12-30 at 14:07 +0100, Philippe Rétornaz wrote:
> > Sorry about being a bit naive, but why it is not possible to do it in
> > two
> > steps ?
> > call stop_machine to put the jmp which skip the call to mcount
> > Then wait until all tasks hits schedule() (synchronize_sched() ?)
> (...)
> There's no way to safely modify two instructions that depend on each
> other in a preemptible kernel, with the exception of waiting for all
> CPUs to hit idle (which may never happen on a busy system). And even
> that may be racy.
> 

Thanks for the detailed explanation, I got it now. I guess the only way would 
be to use the freezer api like freeze_processes() is doing. Looks like it does 
not worth the pain.

Thanks ! 

Philippe


  reply	other threads:[~2011-12-30 23:32 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-29  8:38 ftrace performance impact with different configuration Lei Wen
2011-12-29 15:42 ` Rabin Vincent
2011-12-29 16:21   ` Steven Rostedt
2011-12-30 13:07     ` Philippe Rétornaz
2011-12-30 22:25       ` Steven Rostedt
2011-12-30 23:31         ` Philippe Rétornaz [this message]
2012-01-04 10:06     ` Lei Wen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=2631878.q7bjHk7YBM@laptop \
    --to=philippe.retornaz@epfl.ch \
    --cc=adrian.wenl@gmail.com \
    --cc=leiwen@marvell.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=rabin@rab.in \
    --cc=rostedt@goodmis.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox