linux-kernel - Re: [PATCH v4 0/6] Micro-optimize vclock

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Message-ID: <20110517075635.GA22093@elte.hu>
Date:	Tue, 17 May 2011 09:56:35 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Andy Lutomirski <luto@....EDU>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Borislav Petkov <bp@...64.org>
Subject: Re: [PATCH v4 0/6] Micro-optimize vclock_gettime


* Andi Kleen <andi@...stfloor.org> wrote:

> > And unless you or someone else changes the primitive state of the
> > kernel, framepointers are going to stay simply because removing them
> > breaks profiling backtraces when the hit is inside vread().
> 
> This doesn't work anyways because the glibc stub code calling vgettimeofday 
> normally doesn't set up a frame pointer frame.

But we at least get a callchain back to that point.

Also, Thomas's point remains: you can whine about framepointers and you can try 
to slowly sabotage proper backtraces (nasty and sleazy tactic you are using 
there btw), or you can help out bring sane dwarf support to the kernel.

Thanks,

	Ingo
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