Messages in this thread | | | Subject | Re: Specific support for Intel Atom architecture | From | Andi Kleen <> | Date | Mon, 04 May 2009 09:22:46 +0200 |
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Tobias Doerffel <tobias.doerffel@gmail.com> writes:
> Hi, > > as some of you already might know, work is going on to make GCC fully support > Intel Atom architecture specifics, i.e. make -mtune=atom generate code > optimized for in-order architectures like Intel Atom [1]. > > I therefore started to make up a small patch which adds Intel Atom as a new > processor family which can be selected upon configuration. It's nothing > special and also requires a patched GCC. I'd just like to get some feedback on > it, i.e. is X86_L1_CACHE_SHIFT=6 ok for Atom CPUs (I was not able to find any > information on Atom's cacheline size)?
64bytes.
> Any chance to include this patch once > the Atom patch went into GCC mainline (probably in GCC 4.5)? Any other
atom support already went into gcc mainline.
> objections? > > Please Cc me, I'm not on the list.
FWIW I have a similar patch, but I haven't submitted it yet due to lack of benchmark numbers.
Some comments on yours.
> diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu > index 8130334..8e565b7 100644 > --- a/arch/x86/Kconfig.cpu > +++ b/arch/x86/Kconfig.cpu > @@ -262,6 +262,15 @@ config MCORE2 > family in /proc/cpuinfo. Newer ones have 6 and older ones 15 > (not a typo) > > +config MATOM > + bool "Intel Atom" > + depends on X86_32
This is wrong, There are Atom CPUs which support 64bit code too.
> + > config GENERIC_CPU > bool "Generic-x86-64" > depends on X86_64 > @@ -310,7 +319,7 @@ config X86_L1_CACHE_SHIFT > default "7" if MPENTIUM4 || MPSC > default "4" if X86_ELAN || M486 || M386 || MGEODEGX1 > default "5" if MWINCHIP3D || MWINCHIPC6 || MCRUSOE || MEFFICEON || MCYRIXIII || MK6 || MPENTIUMIII || MPENTIUMII || M686 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODE_LX > - default "6" if MK7 || MK8 || MPENTIUMM || MCORE2 || MVIAC7 || X86_GENERIC || GENERIC_CPU > + default "6" if MK7 || MK8 || MPENTIUMM || MCORE2 || MATOM || MVIAC7 || X86_GENERIC || GENERIC_CPU > > config X86_XADD > def_bool y > @@ -355,11 +364,11 @@ config X86_ALIGNMENT_16 > > config X86_INTEL_USERCOPY > def_bool y > - depends on MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M586MMX || X86_GENERIC || MK8 || MK7 || MEFFICEON || MCORE2 > + depends on MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M586MMX || X86_GENERIC || MK8 || MK7 || MEFFICEON || MCORE2 || MATOM
I don't think that's necessarily a good idea. You would need benchmarks showing that intel user copy performs better on Atom than the original one. Do you have some?
> > config X86_USE_PPRO_CHECKSUM > def_bool y > - depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MK7 || MK6 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MK8 || MVIAC3_2 || MEFFICEON || MGEODE_LX || MCORE2 > + depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MK7 || MK6 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MK8 || MVIAC3_2 || MEFFICEON || MGEODE_LX || MCORE2 || MATOM
Similar here. Atom is quite different from PPro/K8.
> config X86_USE_3DNOW
> config X86_MINIMUM_CPU_FAMILY > int > diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu > index 80177ec..07a11b0 100644 > --- a/arch/x86/Makefile_32.cpu > +++ b/arch/x86/Makefile_32.cpu > @@ -33,6 +33,7 @@ cflags-$(CONFIG_MCYRIXIII) += $(call cc-option,-march=c3,-march=i486) $(align)-f > cflags-$(CONFIG_MVIAC3_2) += $(call cc-option,-march=c3-2,-march=i686) > cflags-$(CONFIG_MVIAC7) += -march=i686 > cflags-$(CONFIG_MCORE2) += -march=i686 $(call tune,core2) > +cflags-$(CONFIG_MATOM) += -march=atom $(call tune,atom) > > # AMD Elan support > cflags-$(CONFIG_X86_ELAN) += -march=i486
That needs to be in the 64bit version too.
> diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h > index 47d6274..e959c4a 100644 > --- a/arch/x86/include/asm/module.h > +++ b/arch/x86/include/asm/module.h > @@ -28,6 +28,8 @@ struct mod_arch_specific {}; > #define MODULE_PROC_FAMILY "586MMX " > #elif defined CONFIG_MCORE2 > #define MODULE_PROC_FAMILY "CORE2 " > +#elif defined CONFIG_MATOM > +#define MODULE_PROC_FAMILY "ATOM "
This should be obsolete anyways, you can just uses CORE2. They have compatible ISAs.
-Andi -- ak@linux.intel.com -- Speaking for myself only.
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