cpuset and affinity implementation

[Daniel Eischen]

On Mon, 25 Feb 2008, Jeff Roberson wrote:

> Binding a processor set to the process simply sets the per-thread binding of 
> each thread in the process.  There is otherwise no specific process binding. 
> We could keep a pointer to the last specifically bound set in the process if 
> we wanted, but what would it be used for other than querying the id of the 
> process?  What if each thread was seperately specifically bound to a 
> different set?  What set should be used on fork? The set of the process or 
> the thread that called fork?  What about when creating a new thread?

The set used on fork should be the set of the calling thread,
same concept as signal masks I would think.  Same thing when
creating a new thread.  I guess I'd check how Linux and Solaris
do it, see if they are consistent.

I can see how you might _not_ want to inherit bindings in a
created thread.  For a process with real-time threads, the
application might start with superuser privileges, create some
threads with real-time priority and set their bindings, then
setuid() to remove superuser privileges.  Is a privilege check
made in a newly created thread when applying inherited bindings?

> See above discussion.  I'm not sure what you mean by 'default' cpuset here.

I imagine the 'default' cpuset as the system's default cpuset,
in lieu of any administratively created cpusets and bindings
for the process (inherited or explicit).

-- 
DE