Re: [PATCH] sched: make update_sd_pick_busiest return true on a busier sd
From: Rik van Riel
Date: Fri Jul 25 2014 - 12:23:38 EST
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On 07/25/2014 12:05 PM, Peter Zijlstra wrote:
> On Fri, Jul 25, 2014 at 11:45:02AM -0400, Rik van Riel wrote:
>>> So for !ASYM the code is effectively:
>>> return sgs->avg_load > sds->busiest_stat.avg_load;
>>> I'd like to at least add a clause that makes overloaded groups
>>> prioritized over !overloaded groups.
>>> Also, like we found earlier, calculate_imbalance() relies on
>>> the sum_nr_running > group_capacity_factor thing, which you've
>>> just 'wrecked', so we'd need an update to that part too.
>> I guess that would mean update_sd_pick_busiest would look like
>> this for the !ASYM case:
>> 1) remembering whether busiest is overloaded
>> 2) if (sgs->busiest_stat.overloaded && !sgs->overloaded) return
>> 3) if (sgs->avg_load > sds->busiest_stat.avg_load) return true;
> Right. So the situation I was worried about is where we have say 8
> +nice tasks in one group and 2 -nice in another. So the group with
> 2 tasks can actually be 'heavier' but not fully utilized. In that
> case we want to pull tasks from the lighter but overloaded group.
I can certainly create a new patch that makes update_sd_pick_busiest
do just that.
Vincent, any objections to me fixing update_sd_pick_busiest now, or
will that conflict with your code cleanups?
All rights reversed
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