Re: [PATCHSET linux-2.6-x86:tip] x86: make percpu offsets zero-based on SMP

From: Brian Gerst
Date: Tue Jan 13 2009 - 08:28:19 EST


On Tue, Jan 13, 2009 at 5:48 AM, Tejun Heo <tj@xxxxxxxxxx> wrote:
> Tejun Heo wrote:
>> Each step was tested with gcc-4.1.3, 4.2.3 and 4.3.1 on x86_64, 4.3.1
>> on i386 for both SMP and UP configurations. The final state is
>> currently being tested using 4.2.3 on both x86_64 and 32.
>
> Aieee.. two sentences mixed up in my head. Correction:
>
> Each step was tested with gcc-4.3.1 for both x86_64 and 32. The final
> step for x86_64 has been tested with gcc-4.1.3, 4.2.3 and 4.3.1.
> Currently, I'm burn-testing both x86_64 and 32 using gcc-4.2.3 with
> all patches applied.
>
> Thanks.

I've been working on a patchset that does something similar, but
eliminating the PDA completely. The start is already in tip/x86/pda.
The plan is to change all PDA variables to be normal per-cpu
variables, merging with 32-bit where possible. Once the PDA is empty,
I'll base %gs at the start of the per-cpu area. I've been working out
the bugs with the last patch (zero-basing the percpu area) before
submitting, but I probably won't have the time until this weekend to
polish it off. I could submit all but the last patch if you'd like.
They are functionally correct, but because the per-cpu area isn't
zero-based yet the generated code is a bit bloated due to having to
calculate the delta for the %gs offset.

--
Brian Gerst
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