[Lazarus] semaphores

[Mark Morgan Lloyd]

Lukasz Sokol wrote:
> On 09/02/2012 11:18, Mark Morgan Lloyd wrote:
>> Lukasz Sokol wrote:
>>> On 09/02/2012 10:01, Sven Barth wrote:
>>>
>>>> The memory that is used by CPU caches is the fastest (but also
>>>> the most expensive that's why it's only used for the relatively
>>>> small caches).
>>>>
>>>> Regards, Sven
>>>>
>>> Is there a way for a non-kernel-developer or plain FPC/Laz user to 
>>> control what is stored in cpu cache ? I thought cache management is
>>> done transparently to userspace...?
>> Only on IA-64 ("Itanic") as far as I know, and in any case for
>> prefetches etc. to be effective the application code would have to be
>> intimately familiar with the details of the hardware implementation.
>> It's the sort of thing that would be a compile-time option on a Cray
>> :-)
>>
> Thought so ;) (disclaimer : I read lkml sometimes stumbling upon devs 
> reordering paddings in structures to make them fit into cachelines)

Which is a special case, since the kernel will have a fairly good idea 
of the platform's capabilities.

The first system I came across with a cache was one of these 
http://www.picklesnet.com/burroughs/images/fullsize/burr0116.jpg circa 
1980. These days I've got things like Suns around the place, and it's 
pretty certain that any assumptions made about x86 cache architecture 
wouldn't apply to those since not only will line length etc. differ but 
so will the relative speeds of the connection between CPU and cache 
compared with cache and main memory.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

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