Re: [tip:sched/core] sched: Lower chances of cputime scaling overflow

From: Frederic Weisbecker
Date: Wed Apr 10 2013 - 11:29:03 EST

2013/4/10 Ingo Molnar <mingo@xxxxxxxxxx>:
> * Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
>> Of course 128 bits ops are very expensive, so to help you evaluating the
>> situation, this is going to happen on every call to task_cputime_adjusted() and
>> thread_group_adjusted(), namely:
> It's really only expensive for divisions. Addition and multiplication should be
> straightforward and relatively low overhead, especially on 64-bit platforms.

Ok, well we still have one division in the scaling path. I'm mostly
worried about the thread group exit that makes use of it through
threadgroup_cputime_adjusted(). Not sure if we can avoid that.
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