Messages in this thread | | | Subject | Re: [Lse-tech] Re: CPU affinity & IPI latency | From | "Shailabh Nagar" <> | Date | Fri, 13 Jul 2001 16:17:42 -0400 |
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David,
> Global scheduling decisions should be triggered in response of load unbalancing > and not at each schedule() run otherwise we're going to introduce a common lock > that will limit the overall scalability.
Thats correct. Though it beggars the question : who will define "load-imbalance" and at what granularity ? In the Loadbalancing extensions to MQ (http://lse.sourceforge.net/scheduling/LB/poolMQ.html) load balancing is done at a frequency specified at the time the loadbalancing module is loaded. The parameter can be changed dynamically through a /proc interface. So we are providing a knob for the user/sysadmin to control the loadbalancing desired.
> My idea about the future of the scheduler is to have a config options users can > chose depending upon the machine use. > By trying to keep a unique scheduler for both UP and MP is like going to give > the same answer to different problems and the scaling factor ( of the scheduler > itself ) on SMP will never improve.
That is true to an extent. It would be convenient for us as scheduler rewriters to have neatly differentiated classes like UP, SMP, BIG_SMP, NUMA etc. But it forces all other scheduler-sensitive code to think of each of these cases separately and is exactly the reason why #ifdef's are discouraged for critical kernel code like the scheduler.
Its certainly a challenge to provide SMP/NUMA scalability in the scheduler (and elsewhere in the kernel) without having to resort to an #ifdef.
Shailabh
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