linux-kernel - Re: [PATCH v3 5/6] x86-64: Move vread_tsc into a new file with sensible options

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Message-ID: <1305038162.2914.93.camel@laptop>
Date:	Tue, 10 May 2011 16:36:02 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andy Lutomirski <luto@....EDU>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3 5/6] x86-64: Move vread_tsc into a new file with
 sensible options

On Tue, 2011-05-10 at 10:15 -0400, Andy Lutomirski wrote:
> vread_tsc is short and hot, and it's userspace code so the usual
> reasons to keep frame pointers around, enable -pg, and turn off
> sibling calls don't apply.
> 
I really don't like that, turning off frame pointers here means that if
your profiler interrupt hits while in the vDSO the user-space backtrace
is dead.

Please leave the frame pointer in. Esp on x86_64 the cost of keeping the
framepointer isn't much at all since it isn't nearly as register starved
as i386.

I'm fine with stripping -pg, that is indeed useless for the vDSO.

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