Re: [RFC 00/15] x86_64: Optimize percpu accesses

[Eric W. Biederman]

Jeremy Fitzhardinge <jeremy@xxxxxxxx> writes:

> Eric W. Biederman wrote:
>> I think we can get away with just simply realloc'ing the percpu area
>> on each cpu.  No fancy table manipulations required.  Just update
>> the base pointer in %gs and in someplace global.
>>
>
> It's perfectly legitimate to take the address of a percpu variable and store it
> somewhere.  We can't move them around.

Really?  I guess there are cases where that makes sense.  It is a pretty
rare case though.  Especially when you are not talking about doing it temporarily
with preemption disabled.  There are few enough users of the API I think we can
certainly explore the cost of forbidding in the general case of storing the
address of a percpu variable.

Eric

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