Messages in this thread |  | | From | Erich Focht <> | Subject | Re: [patch] HT scheduler, sched-2.5.59-E2 | Date | Tue, 4 Feb 2003 10:31:20 +0100 |
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Hi Ingo,
On Monday 03 February 2003 19:23, Ingo Molnar wrote: > -#define > CAN_MIGRATE_TASK(p,rq,this_cpu) \ > - ((jiffies - (p)->sleep_timestamp > cache_decay_ticks) && \ > - !task_running(rq, p) && \ > - ((p)->cpus_allowed & (1UL << (this_cpu)))) +#define > CAN_MIGRATE_TASK(p,rq,cpu) \ > + ((idle || (jiffies - (p)->last_run > cache_decay_ticks)) && \ > + !task_running(p) && task_allowed(p, cpu))
at least for NUMA systems this is too aggressive (though I believe normal SMP systems could be hurt, too).
The problem: freshly forked tasks are stolen by idle cpus on the same node before they exec. This actually disables the sched_balance_exec() mechanism as the tasks to be balanced already run alone on other CPUs. Which means: the whole benefit of having balanced nodes (maximize the memory bandwidth) is gone.
The change below is less aggressive but in the same philosophy. Could you please take it instead?
> CAN_MIGRATE_TASK(p,rq,cpu) \ > + ((jiffies - (p)->last_run > (cache_decay_ticks >> idle)) && \ > + !task_running(p) && task_allowed(p, cpu))
Regards, Erich
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