From: Ingo Molnar <mingo@elte.hu>
To: Lee Revell <rlrevell@joe-job.com>
Cc: Philippe Elie <phil.el@wanadoo.fr>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Oops with oprofile + RT preempt 2.6.11-rc2-RT-V0.7.37-01
Date: Thu, 17 Feb 2005 21:11:45 +0100 [thread overview]
Message-ID: <20050217201145.GA14706@elte.hu> (raw)
In-Reply-To: <1108670727.11411.6.camel@krustophenia.net>
* Lee Revell <rlrevell@joe-job.com> wrote:
> I noticed profiling the kernel with PREEMPT_DESKTOP that mcount and
> __mcount add quite a bit of overhead. Something like .5% CPU each.
> Sorry, I didn't save the oprofile output.
>
> So, disable CONFIG_MCOUNT if you want minimal overhead from the RT
> patches. IIRC it was previously stated that the latency tracing
> overhead could be mostly avoided by disabling it at runtime.
yes - most of the overhead can be disabled, but not all. 1% CPU time
might sound alot but when compared against 10% (or more) tracing
overehad it's small. The least overhead comes from disabling tracing in
the .config.
Ingo
next prev parent reply other threads:[~2005-02-17 20:13 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-13 6:07 Oops with oprofile + RT preempt 2.6.11-rc2-RT-V0.7.37-01 Lee Revell
2005-02-13 13:00 ` Philippe Elie
2005-02-13 13:30 ` Ingo Molnar
2005-02-14 0:55 ` Lee Revell
2005-02-14 1:16 ` Dave Jones
2005-02-17 20:05 ` Lee Revell
2005-02-17 20:11 ` Ingo Molnar [this message]
2005-02-13 13:02 ` Ingo Molnar
2005-02-13 13:15 ` Peter Zijlstra
2005-02-13 13:16 ` Ingo Molnar
2005-02-13 13:20 ` Peter Zijlstra
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