On 21 June 2013 16:38, Arjan van de Ven arjan@linux.intel.com wrote:
On 6/21/2013 1:50 AM, Morten Rasmussen wrote:
A hint when a task is moved to a new cpu is too late if the migration shouldn't have happened at all. If the scheduler knows that the cpu is able to switch to a higher p-state it can decide to wait for the p-state change instead of migrating the task and waking up another cpu.
oops sorry I misread your mail (lack of early coffee I suppose)
I can see your point of having a thing for "did we ask for all the performance we could ask for" prior to doing a load balance (although, for power efficiency, if you have two tasks that could run in parallel, it's usually better to run them in parallel... so likely we should balance anyway)
Not necessarily, especially if parallel running implies powering up a full cluster just for one CPU (it depends on the hardware but for example a cluster may not be able to go in deeper sleep states unless all the CPUs in that cluster are idle).
-- Catalin