Re: Slowdown with randomize_va_space in 188.8.131.52
From: Andrew Morton
Date: Fri Jul 29 2005 - 20:25:55 EST
Eric Lammerts <eric@xxxxxxxxxxxx> 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@xxxxxxxxxx> 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
> What about this patch?
It has the virtue of simplicity. Arjan, were you planning on anything
> --- 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 & 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)
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