linux-kernel - Re: [PATCH 0/8] livepatch: klp-convert tool

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Date:   Fri, 20 Oct 2017 15:39:49 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     Torsten Duwe <duwe@....de>, Joao Moreira <jmoreira@...e.de>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        mmarek@...e.cz, pmladek@...e.com, jikos@...e.cz, nstange@...e.de,
        jroedel@...e.de, matz@...e.de, khlebnikov@...dex-team.ru,
        jeyu@...nel.org
Subject: Re: [PATCH 0/8] livepatch: klp-convert tool


> > For -fpatchable-function-entries I switched
> > off IPA-RA, as especially on RISC there's _nothing_ you can do between
> > functions without at least one scratch reg. But for live patching, I'd like
> > the kernel to be compiled in the first place with 100% ABI adherence, IOW
> > all IPA optimisations turned off. Does anyone have numbers on the performance
> > impact?
> 
> I agree that would be the best option.
> 
> I don't think anyone has measured it because we don't know how to get
> the compiler to do that :-)  My guess is that it will be something close
> to negligible.

I asked Nicolai to do some performance testing with all the options that 
could be disabled disabled.

Miroslav