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From: John Kacur <jkacur@redhat.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org
Subject: Re: [performance problem] CONFIG_DYNAMIC_FTRACE: Increased kernel  build times
Date: Fri, 23 Oct 2009 12:18:41 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.00.0910231211540.3549@localhost.localdomain> (raw)
In-Reply-To: <520f0cf10910230307k91d0c80sa3d69bcd74d6e1f1@mail.gmail.com>

[-- Attachment #1: Type: TEXT/PLAIN, Size: 879 bytes --]

2009/10/23 Ingo Molnar <mingo@elte.hu> wrote:
> 
> Steve,
> 
> i did an 64-bit allyesconfig build test (with debug_info disabled), with
> and without CONFIG_DYNAMIC_FTRACE set.
> 
> The build time results are:
> 
>  -CONFIG_DYNAMIC_FTRACE:   266.30
>  +CONFIG_DYNAMIC_FTRACE:   296.07 (+11.2%)
> 
> So we get more than 10% build time overhead.
> 
> That's quite high - higher than what i remember having measured
> originally when the first iteration of the mcount code went in.
> 
> This extra overhead comes from the mcount post-processing script
> (scripts/recordmcount.pl) that runs objcopy as well and is written in
> Perl. I think this whole angle needs to be improved - 10% is way too
> high of a price to pay.

Hi Ingo, do you still have the profiling data to share with us?
Was the problem more in objcopy / objdump, rather than in the perl script 
itself?

Thanks

John

  parent reply	other threads:[~2009-10-23 10:19 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-10-23  7:45 Ingo Molnar
     [not found] ` <520f0cf10910230307k91d0c80sa3d69bcd74d6e1f1@mail.gmail.com>
2009-10-23 10:18   ` John Kacur [this message]
2009-10-23 10:37     ` Ingo Molnar
2009-10-23 13:18 ` Steven Rostedt

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