Messages in this thread | | | Subject | Re: [PATCH] sched: fix lose fair sleeper bonus in switch_to_fair() | From | Wanpeng Li <> | Date | Tue, 8 Sep 2015 14:55:20 +0800 |
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On 9/8/15 10:10 AM, Byungchul Park wrote: > hello wanpeng, > > On Mon, Sep 07, 2015 at 05:45:20PM +0800, Wanpeng Li wrote: >> The sleeper task will be normalized when moved from fair_sched_class, in >> order that vruntime will be adjusted either the task is running or sleeping >> when moved back. The nomalization in switch_to_fair for sleep task will >> result in lose fair sleeper bonus in place_entity() once the vruntime - >> cfs_rq->min_vruntime is big when moved from fair_sched_class. > it is nothing to do with normalization. > > if vruntime - cfs_rq->min_vruntime is big even though place_entity() was > called when moved from fair class, then we actually expect that it still has > a big vruntime when moved back to fair class. > > if we don't expect that it still has a big vruntime when moved back to fair > class, we need to consider other approaches e.g. to move a position calling > place_entity() or to add place_entity() call properly .. > > however we should not touch normalization logic. in other words, if we > normalized the vruntime when leaved, then we should necessarily restore the > vruntime to a non-normalized value when moved back.
Not about vruntime - cfs_rq->min_vruntime is big, I think my patch description above is confusing, and what's wrong I found is explained in the mail which reply to Peterz.
> >> This patch fix it by adjusting vruntime just during migrating as original >> codes since the vruntime of the task has usually NOT been normalized in >> this case. > could you explain this in detail? when is a vruntime not normalized? >
The comments in task_move_group_fair() which you removed in your commit:
| * When !queued, vruntime of the task has usually NOT been normalized
Regards, Wanpeng Li
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