Re: Slowdown with randomize_va_space in 2.6.12.2

[Andrew Morton <akpm@osdl.org>]

Eric Lammerts <eric@lammerts.org> wrote:
>
> 
> On Thu, 7 Jul 2005, Arjan van de Ven wrote:
> > On Wed, 2005-07-06 at 18:12 -0700, Andrew Morton wrote:
> > > Dave Jones <davej@redhat.com> wrote:
> > > > On Transmeta CPUs that probably triggers a retranslation of
> > > > x86->native bytecode, if it thinks it hasn't seen code at that
> > > > address before.
> > >
> > > ouch.   What do we do?  Default to off?  Default to off on xmeta?
> >
> > off-on-xmeta would be my preference; I'll cook up a patch for that.
> 
> It would be nice if a fix for this could get in before 2.6.13 comes
> out.

I agree.

> What about this patch?
> 

It has the virtue of simplicity.  Arjan, were you planning on anything
fancier?

> 
> --- linux-2.6.13-rc4/arch/i386/kernel/cpu/transmeta.c.orig	2005-06-17 15:48:29.000000000 -0400
> +++ linux-2.6.13-rc4/arch/i386/kernel/cpu/transmeta.c	2005-07-29 20:46:54.000000000 -0400
> @@ -76,6 +76,10 @@
>  #define USER686 (X86_FEATURE_TSC|X86_FEATURE_CX8|X86_FEATURE_CMOV)
>          if ( c->x86 == 5 && (c->x86_capability[0] & USER686) == USER686 )
>  		c->x86 = 6;
> +
> +	/* randomize_va_space slows us down enormously;
> +	   it probably triggers retranslation of x86->native bytecode */
> +	randomize_va_space = 0;
>  }
> 
>  static void transmeta_identify(struct cpuinfo_x86 * c)