linux-kernel - Re: [PATCH 0/7] perf, x86: Haswell LBR call stack support

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Message-ID: <20130626164027.GE6123@two.firstfloor.org>
Date:	Wed, 26 Jun 2013 18:40:27 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Yan, Zheng" <zheng.z.yan@...el.com>, linux-kernel@...r.kernel.org,
	mingo@...nel.org, eranian@...gle.com, andi@...stfloor.org
Subject: Re: [PATCH 0/7] perf, x86: Haswell LBR call stack support

> So on pretty much every program you'd be lucky to get the top of the
> callstack but can end up with nearly nothing.

The last few entries up are usually the interesting ones, and those will
be preserved.

Do you really care about main() for profiling?

When you pop back up there may be a few situations where you
have a very small visible stack, but as soon as the program
starts nesting deeper again that will be fixed.

> Given that, and the other limitations I don't think its a fair
> replacement for user callchains.

It's not intended to be a full replacement, just to cover
cases that cannot give you callgraphs at all today.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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