Re: i915.ko WC writes are slow after ea8596bb2d8d379

From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: i915.ko WC writes are slow after ea8596bb2d8d379
Date	2015-11-19 09:20 +0100
Message-ID	<qwsBK-6MQ-29@gated-at.bofh.it> (permalink)
References	<o8VpT-1dR-1@gated-at.bofh.it> <o8WvE-2R6-17@gated-at.bofh.it> <qwcng-4gQ-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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* Chris Wilson <chris@chris-wilson.co.uk> wrote:

> > > A bisection pointed to 
> > > 
> > > commit ea8596bb2d8d37957f3e92db9511c50801689180
> > > Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> > > Date:   Thu Jul 18 20:47:53 2013 +0900
> > > 
> > >     kprobes/x86: Remove unused text_poke_smp() and text_poke_smp_batch() functions
> > > 
> > > of which the active ingredient was just
> > > 
> > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > > index b32ebf9..f4001e0 100644
> > > --- a/arch/x86/Kconfig
> > > +++ b/arch/x86/Kconfig
> > > @@ -2334,7 +2334,6 @@ config HAVE_ATOMIC_IOMAP
> > >  
> > >  config HAVE_TEXT_POKE_SMP
> > >         bool
> > > -       select STOP_MACHINE if SMP

Ouch...

This is certainly an educative example of how pure 'code removal' patches can have 
unintended side effects.

Is there a full fix patch available, and is anyone pushing that to Linus?

Thanks,

	Ingo
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Re: i915.ko WC writes are slow after ea8596bb2d8d379 Chris Wilson <chris@chris-wilson.co.uk> - 2015-11-18 16:00 +0100
  Re: i915.ko WC writes are slow after ea8596bb2d8d379 Andy Lutomirski <luto@amacapital.net> - 2015-11-18 17:00 +0100
    Re: i915.ko WC writes are slow after ea8596bb2d8d379 Ingo Molnar <mingo@kernel.org> - 2015-11-19 09:20 +0100
      [PATCH] kernel: Remove stop_machine() Kconfig dependency Chris Wilson <chris@chris-wilson.co.uk> - 2015-11-19 11:10 +0100
  Re: i915.ko WC writes are slow after ea8596bb2d8d379 Ingo Molnar <mingo@kernel.org> - 2015-11-19 09:20 +0100

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