Re: [PATCH] sched: smpnice try to wakeup modification

[Tim Chen <tim.c.chen@linux.intel.com>]

Peter Williams wrote:
> Tim Chen wrote:
>> Peter,
>>
>> If there is no load on this_cpu, (i.e. tl_per_task is 0), we will 
>> fail the  "tl + target_load(cpu, idx) <= tl_per_task" check.
>
> This isn't the case.  If this_cpu is idle tl_per_task will be set to 
> SCHED_LOAD_SCALE (see implementation of cpu_avg_load_per_task()) and 
> that expression should succeed unless the value returned by 
> target_load(cpu, idx) is bigger than SCHED_LOAD_SCALE.  This is 
> exactly the same as would have happened with the original code.
>
> (BTW cpu_avg_load_per_task()'s original implementation would have had 
> the effect you describe but it was modified when it was realized that 
> it would break the code in a lot of places (not just here).  The 
> thinking now is that if there isn't enough data available to calculate 
> the average load per task for a run queue then the correct value to 
> use is the theoretical average i.e. SCHED_LOAD_SCALE.)
>
Ah, I was looking at the original smpnice patch.  Thanks for clarifying.

Tim