linux-kernel - Re: [PATCH 1/2] perf: Pass appropriate frame pointer to dump

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Date:	Thu, 31 Dec 2009 07:13:54 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 1/2] perf: Pass appropriate frame pointer to
	dump_trace()

On Thu, Dec 31, 2009 at 05:53:02AM +0100, Frederic Weisbecker wrote:
> Pass the frame pointer from the regs of the interrupted path
> to dump_trace() while processing the stack trace.
> 
> Currently, dump_trace() takes the current bp and starts the
> callchain from dump_trace() itself. This is wasteful because
> we need to walk through the entire NMI/DEBUG stack before
> retrieving the interrupted point.
> 
> We can fix that by just using the frame pointer from the captured
> regs. It points exactly where we want to start.



BTW, another effect of this patch: we didn't have the
nmi/debug stack frame filtering in x86-32. So the callchains
were polluted by the perf_callchain path, do_debug and so
on...

After this patch we don't need this filtering anymore
as the nmi/debug frames are zapped. It becomes clean
like in x86-64.

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