support for only 255 processes on a 405

support for only 255 processes on a 405

[Ralph Blach]

Is there any support for having a special case for the 405 that would
limit the number of processes to 255.  This means that the pid and
context could be the same.  This might be a performance gain.

Chip

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Re: support for only 255 processes on a 405

[Dan Malek]

Ralph Blach wrote:
>
> Is there any support for having a special case for the 405 that would
> limit the number of processes to 255.  This means that the pid and
> context could be the same.  This might be a performance gain.

The PID and context are already reused until there are more than 255
(or whatever the MMU can support) active processes.  There isn't a
special case needed, this is generic to all PowerPC with small context
space resources.


	-- Dan

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Re: support for only 255 processes on a 405

[Ralph Blach]

Dan

Perhaps i dont understand.  It looks like from the code that process id
and pids dont match.  Could you explain how this code works.

Chip

Dan Malek wrote:
>
> Ralph Blach wrote:
> >
> > Is there any support for having a special case for the 405 that would
> > limit the number of processes to 255.  This means that the pid and
> > context could be the same.  This might be a performance gain.
>
> The PID and context are already reused until there are more than 255
> (or whatever the MMU can support) active processes.  There isn't a
> special case needed, this is generic to all PowerPC with small context
> space resources.
>
>         -- Dan

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

Re: support for only 255 processes on a 405

[Dan Malek]

Ralph Blach wrote:

> Perhaps i dont understand.  It looks like from the code that process id
> and pids dont match.  Could you explain how this code works.

The "contexts" are associated with an MM context, not with a process ID.
Typically a process has one MM context, but there are cases (like
multithreaded address spaces) that will share an MM context and all
get the same TLB context.  A "process" is somewhat blurry in Linux,
but you can still think of it as an address space plus a processor
thread.  We are really concerned what happens to the address space
and how that affects the MMU, not what the thread actually does,
or how many share the address space.


	-- Dan

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