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From: Andy Lutomirski <luto@amacapital.net>
Date: Tue, 21 Jul 2015 21:39:23 -0700
Message-ID: <CALCETrXQfj4zivN6Fbioesx6mw6ovZEZoR8DJdEghQ2BTpWwPA@mail.gmail.com>
Subject: Re: [RFC PATCH 04/21] x86/hweight: Add stack frame dependency for __arch_hweight*()
To: Borislav Petkov <bp@alien8.de>
Cc: Michal Marek <mmarek@suse.cz>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Josh Poimboeuf <jpoimboe@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>, Pedro Alves <palves@redhat.com>,
        live-patching@vger.kernel.org, X86 ML <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>
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On Tue, Jul 21, 2015 at 9:25 PM, Borislav Petkov <bp@alien8.de> wrote:
> On Tue, Jul 21, 2015 at 05:13:12PM -0700, Andy Lutomirski wrote:
>> Enough for oopses, perhaps, but maybe not enough for perf.
>>
>> It sounds like you want CFI unwinding :)
>
> What would you want to unwind in those __sw_hweight* almost-trivial,
> tail functions?

So your shiny perf profile shows cumulative time in whatever called
them.  Sure, this is arguably silly if we're stuck with frame
pointers.

--Andy
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