Re: BUG #2401: spinlocks not available on amd64

The amd64 spintlock instructions use no AMD-specific features.  It's
base intel 64bit instruction set.  We ship a product with similar such
spin locks and have never had an issue across a large variety of
chipsets (Intel, AMD, and virtualized).

In short, if you can actually run 64bit code, the CAS stuff should
just work.

On Jun 24, 2009, at 8:27 AM, Gregory Stark wrote:

>
> Theo Schlossnagle wrote:
>
>> Tom Lane wrote:
>>
>>> There is no reason for the i386 or AMD64 code to be different from
>>> what's
>>> already tested on Linux --- the hardware's the same and the OS
>>> surely
>>> doesn't make a difference at this level.
>>
>> On linux you use gcc, which allows for inline assembly. So, the
>> code is
>> already very different.
>
> How does this interact with binary builds such as rpms? If someone
> installs an
> amd64 binary on an x86 machine or vice versa does this assembly do
> the right
> thing at all? Does it perform slowly?
>
> Ideally we would compile both and pick the right one at run-time but
> that
> might have annoying overhead if there's a branch before every
> pg_atomic_cas
> call.
>
> Perhaps a minimal thing to do would be to detect a mismatch on
> startup and log
> a message about it.
>
> --
>  Gregory Stark
>  http://mit.edu/~gsstark/resume.pdf

--
Theo Schlossnagle
http://omniti.com/is/theo-schlossnagle
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