Messages in this thread Patch in this message | | | Date | Tue, 10 Jan 2006 18:28:02 +0000 | From | Coywolf Qi Hunt <> | Subject | Re: 2G memory split |
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2006/1/10, Jens Axboe <axboe@suse.de>: > On Tue, Jan 10 2006, Byron Stanoszek wrote: > > On Tue, 10 Jan 2006, Jens Axboe wrote: > > > > >>yes, i made it totally configurable in 2.4 days: 1:3, 2/2 and 3:1 splits > > >>were possible. It was a larger patch to enable all this across x86, but > > >>the Kconfig portion was removed a bit later because people _frequently_ > > >>misconfigured their kernels and then complained about the results. > > > > > >How is this different than all other sorts of misconfigurations? As far > > >as I can tell, the biggest "problem" for some is if they depend on some > > >binary module that will of course break with a different page offset. > > > > > >For simplicity, I didn't add more than the 2/2 split, where we could add > > >even a 3/1 kernel/user or a 0.5/3.5 (I think sles8 had this). > > > > I prefer setting __PAGE_OFFSET to (0x78000000) on machines with 2GB of RAM. > > This seems to let the kernel use the full 2GB of memory, rather than just > > 1920-1984 MB (at least back in 2.4 days). > > A newer version, trying to cater to the various comments in here. > Changes: > > - Add 1G_OPT split, meant for 1GiB machines. Uses 0xB0000000 > - Add 1G/3G split > - Move the 2G/2G a little, so the full 2GiB of ram can be mapped. > - Improve help text (I hope :) > - Make option depend on EXPERIMENTAL. > - Make the page.h a lot more readable. > > --- > > Add option for configuring the page offset, to better optimize the > kernel for higher memory machines. Enables users to get rid of high > memory for eg a 1GiB machine. > > Signed-off-by: Jens Axboe <axboe@suse.de> > > diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig > index d849c68..fcad8f7 100644 > --- a/arch/i386/Kconfig > +++ b/arch/i386/Kconfig > @@ -444,6 +464,32 @@ config HIGHMEM64G > > endchoice > > +choice > + depends on NOHIGHMEM && EXPERIMENTAL > + prompt "Memory split" > + default DEFAULT_3G > + help > + Select the wanted split between kernel and user memory. > + > + If the address range available to the kernel is less than the > + physical memory installed, the remaining memory will be available > + as "high memory". Accessing high memory is a little more costly > + than low memory, as it needs to be mapped into the kernel first. > + > + Note that selecting anything but the default 3G/1G split will make > + your kernel incompatible with binary only modules. > + > + config DEFAULT_3G > + bool "3G/1G user/kernel split" > + config DEFAULT_3G_OPT > + bool "3G/1G user/kernel split (for full 1G low memory)" > + config DEFAULT_2G > + bool "2G/2G user/kernel split" > + config DEFAULT_1G > + bool "1G/3G user/kernel split"
I don't like these names. Can't your invent better ones? Having multiple defaults seems odd. See these maybe:
MEMSPLIT_U3_K1 MEMSPLIT_U11_K5 MEMSPLIT_U39_K44 MEMSPLIT_U1_K3
odd too? midnight here. |-)
> + > +endchoice > + > config HIGHMEM > bool > depends on HIGHMEM64G || HIGHMEM4G > diff --git a/include/asm-i386/page.h b/include/asm-i386/page.h > index 73296d9..7da50a1 100644 > --- a/include/asm-i386/page.h > +++ b/include/asm-i386/page.h > @@ -109,11 +109,23 @@ extern int page_is_ram(unsigned long pag > > #endif /* __ASSEMBLY__ */ > > +#if defined(CONFIG_DEFAULT_3G) > +#define __PAGE_OFFSET_RAW (0xC0000000) > +#elif defined(CONFIG_DEFAULT_3G_OPT) > +#define __PAGE_OFFSET_RAW (0xB0000000) > +#elif defined(CONFIG_DEFAULT_2G) > +#define __PAGE_OFFSET_RAW (0x78000000) > +#elif defined(CONFIG_DEFAULT_1G) > +#define __PAGE_OFFSET_RAW (0x40000000) > +#else > +#error "Bad user/kernel offset" > +#endif > + > #ifdef __ASSEMBLY__ > -#define __PAGE_OFFSET (0xC0000000) > +#define __PAGE_OFFSET __PAGE_OFFSET_RAW > #define __PHYSICAL_START CONFIG_PHYSICAL_START > #else > -#define __PAGE_OFFSET (0xC0000000UL) > +#define __PAGE_OFFSET ((unsigned long)__PAGE_OFFSET_RAW) > #define __PHYSICAL_START ((unsigned long)CONFIG_PHYSICAL_START) > #endif > #define __KERNEL_START (__PAGE_OFFSET + __PHYSICAL_START) > > -- > Jens Axboe > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
-- Coywolf Qi Hunt - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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