linux-kernel - Re: [patch 15/14] x86/dumpstack/64: Speedup in_exception

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Message-ID: <20190402155149.c23ivzzc5hyykokl@treble>
Date:   Tue, 2 Apr 2019 10:51:49 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [patch 15/14] x86/dumpstack/64: Speedup in_exception_stack()

On Tue, Apr 02, 2019 at 05:48:56PM +0200, Thomas Gleixner wrote:
> > With the above "(stk <= begin || stk >= end)" check, removing the loop
> > becomes not all that important since exception stack dumps are quite
> > rare and not performance sensitive.  With all the macros this code
> > becomes a little more obtuse, so I'm not sure whether removal of the
> > loop is a net positive.
> 
> What about perf? It's NMI context and probably starts from there. Peter?

I believe perf unwinds starting from the regs from the context which was
interrupted by the NMI.

-- 
Josh