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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This archive was generated by hypermail 2b29 : Fri Feb 07 2003 - 22:00:14 EST