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

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Date:	Tue, 13 Jan 2009 08:27:52 -0500
From:	"Brian Gerst" <brgerst@...il.com>
To:	"Tejun Heo" <tj@...nel.org>
Cc:	ebiederm@...ssion.com, cl@...ux-foundation.org,
	rusty@...tcorp.com.au, mingo@...e.hu, travis@....com,
	linux-kernel@...r.kernel.org, hpa@...or.com,
	akpm@...ux-foundation.org, steiner@....com, hugh@...itas.com
Subject: Re: [PATCHSET linux-2.6-x86:tip] x86: make percpu offsets zero-based on SMP

On Tue, Jan 13, 2009 at 5:48 AM, Tejun Heo <tj@...nel.org> 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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