Re: mutexes, locks and so on...

[Matt Thomas <matt%3am-software.com@localhost>]

On Nov 12, 2010, at 6:39 AM, Joerg Sonnenberger wrote:

> On Fri, Nov 12, 2010 at 03:25:04PM +0100, Johnny Billquist wrote:
>> So what you are arguing is that MI needn't be so much MI anymore,
>> and that supporting anything more than mainstream today is more to
>> be considered a lucky accident than a desired goal?
> 
> It is not about mainstream. Please tell me one architecture that has
> been created in the last 10 years, supports at least 32bit address
> space, virtual memory and doesn't support either CAS or LL/SC. I would
> be very surprised if there is one. Like I said, there has been a lot of
> research into scalable primitives and algorithms and processor design
> has changed accordingly. The ras-like UP implementation of CAS is almost
> free as long as your interrupt rate is much lower than the rate of CAS
> operations. There are a lot of low hanging fruits for VAX like providing
> proper assembler versions of the atomic add etc, which sound feasible
> from the docs I found. There are other areas where VAX hasn't kept up
> with the "mainstream" architectures. pmap_growkernel to name one with
> practical implications.

atomic_add isn't possible since ADAWI is only 16 bits and then you have
to worry about carry to the upper word.

pmap_growkernel isn't really practical to the way the VAX MMU works
since it needs contiguous physical pages for the system page table.