linux-kernel - Re: [PATCH 7/7] DWARF: add the config option

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Message-ID: <20170523070701.hxalap5q54nrn6z5@hirez.programming.kicks-ass.net>
Date:   Tue, 23 May 2017 09:07:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        live-patching@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 7/7] DWARF: add the config option

On Wed, May 10, 2017 at 10:32:06AM +0200, Jiri Slaby wrote:
> > But it does hurt, in the sense that the complicated format of DWARF CFI
> > means the unwinder has to jump through a lot more hoops to read it.
> 
> Why that matters, actually? Unwinder is nothing to be performance
> oriented. And if somebody is doing a lot of unwinding during runtime,
> they can switch to in-this-case-faster FP unwinder.

perf (and ftrace) like the unwinder to be considered performance
oriented.