> On 04/07/2010 09:48 AM, Himanshu Aggarwal wrote:
>> I think for some architectures, the position of highmem is constrained
>> by hardware as well. It is not always a kernel decision and not always
>> configurable as in case of x86.
>
>
> This is correct.
>
>> In case of MIPS32, low memory is between 0 and 512 MB and high memory
>> starts above 512 MB. Also the user space is of size 2 GB.
>>
>> Please see the definition of macros PAGE_OFFSET and HIGHMEM_START at :
>>
http://lxr.linux.no/linux+v2.6.33/arch/mips/include/asm/mach-generic/spaces.h
>
> Right so far...
>
>> This is because MIPS32 processors have KSEG0 and KSEG1 segments lying
>> between 0 and 512 MB and KSEG2/3 lies above it.
>>
>> May be someone on the group can confirm this.
>
> Wrong. I have to say this thread has been just astonishing in the
> amount of misinformation.
>
> On MIPS32, userspace is 0-2 GB, kseg0 is 2.0-2.5 GB and kseg1 is 2.5-3.0
> GB. kseg2/3 (3.0-4.0 GB), which invokes the TLB, is used for the
> vmalloc/iomap/kmap area.
>
> LOWMEM has to fit inside kseg0, so LOWMEM is limited to 512 MB in thie
> current Linux implementation.
