Re: [RFC/RFT PATCH v3] sched: automated per tty task groups

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Fri, 2010-11-19 at 01:07 +0100, Samuel Thibault wrote:
> 
> 
> Also note that having a hierarchical process structure should permit to
> make things globally more efficient: avoid putting e.g. your cpp, cc1,
> and asm processes at three corners of your 4-socket NUMA machine :) 

We have the hierarchy mandated by POSIX to track parents, childs,
sessions and all that stuff, its just not the data structure used for
scheduling.

And no, using that to load-balance between CPUs doesn't necessarily help
with the NUMA case, load-balancing is an impossible job (equivalent to
page-replacement -- you simply don't know the future), applications
simply do wildly weird stuff. 

>From a process hierarchy there's absolutely no difference between a
cc1/cpp/asm and some MPI jobs, both can be parent-child relations with
pipes between, some just run short and have data affinity, others run
long and don't have any.