Re: [PATCH v3 3/7] sched: throttle cfs_rq entities which exceedtheir local quota

[KAMEZAWA Hiroyuki]

On Thu, 14 Oct 2010 11:12:22 +0200
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> On Wed, 2010-10-13 at 15:34 +0900, KAMEZAWA Hiroyuki wrote:
> > cpu.share and bandwidth control can't be used simultaneously or...
> > is this fair ? I'm not familiar with scheduler but this allows boost this tg.
> > Could you add a brief documentaion of a spec/feature. in the next post ?
> 
> Like explained, shares control the proportional distribution of time
> between groups, bandwidth puts a limit on how much time a group can
> take. It can cause a group to receive less than its fair share, but
> never more.
> 
> There is, however, a problem with all this, and that is that all this
> explicit idling of tasks can lead to a form of priority inversion.
> Regular preemptive scheduling already suffers from this, but explicitly
> idling tasks exacerbates the situation.
> 
> You basically get to add the longest induced idle time to all your lock
> hold times.
> 

What is the user-visible difference of the problem between
  1) limit share to be very small.
  2) use throttole.

If share is used, lock-hodler's priority is boosted ?

Thanks,
-Kame

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