Re: Gang Scheduling in linux

[Richard Gooch]

Hubertus Franke writes:
> On a single SMP I could imagine for instance for parallel reendering
> or similar tightly integrated parallel programs that need data
> synchronization.  Most of these apps assume a tightly coupled
> non-virtual resource, i.e., scheduling of tasks is aligned.
> 
> SGI used to have that stuff in their base kernel. Read a paper about
> this some years ago.  Again, at the beginning I'd go with a user
> level scheduler approach that certainly would satisfy national labs
> etc. Most of the cluster schedulers, like PBS and LoadLeveler etc.,
> already provide that functionality.

A completely user-level solution may have some disadvantages, though,
such as delays in scheduling on/off (say if some daemon is used to
scan the process list). Perhaps we could add a small hack to the
scheduler such that when a task is about to be scheduled off, a signal
can be sent to a designated pid? Similarly, when a task is scheduled
on, another signal may be sent. An application that wanted to have
gang scheduling could then make use of this to STOP/CONT threads.

				Regards,

					Richard....
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