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SubjectRe: hammer: MAP_32BIT
Timothy Miller wrote:
>>
>> The purpose is that there is a slight task-switching speed advantage if
>> the address is in the bottom 4 GB. Since this affects every process,
>> and most processes use very little TLS, this is worthwhile.
>>
>> This is fundamentally due to a K8 design flaw.
>
> Is there an explicit check somewhere for this? Are the page tables laid
> out differently?
>

No, there are two ways to load the FS base register: use a descriptor,
which is limited to 4 GB but is faster, or WRMSR, which is slower, but
unlimited.

-hpa

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