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SubjectRe: [RFC 00/15] x86_64: Optimize percpu accesses
Christoph Lameter wrote:
>> The nice thing about the non-zero-based scheme i386 uses is that setting
>> gs-base to zero means that percpu variables accesses get directly to the
>> prototype percpu data area, which simplifies boot time setup (which is
>> doubly awkward on 32-bit because you need to generate a GDT entry rather
>> than just load an MSR as you do in 64-bit).
>>
>
> Great but it causes trouble in other ways as discussed.

What other trouble? It works fine.

> Its best to consistently access
> per cpu variables using the segment registers.
>


It is, but initially the segment base is 0, so just using a percpu
variable does something sensible from the start with no special setup.

J


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