Re: [PATCH V4 05/15] blk-throttle: add downgrade logic

From: Shaohua Li
Date: Tue Nov 22 2016 - 18:38:45 EST

On Tue, Nov 22, 2016 at 04:42:00PM -0500, Tejun Heo wrote:
> Hello,
> On Tue, Nov 22, 2016 at 04:21:21PM -0500, Tejun Heo wrote:
> > 1. A cgroup and its high and max limits don't have much to do with
> > other cgroups and their limits. I don't get how the choice between
> > high and max limits can be a td-wide state.
> Ah, okay, this combines with idle cgroup detection to determine
> whether the cgroups should be allowed to exceed high limits. It makes
> more sense to me now. In that case, for the high/max limit range
> issues, the enforced high/max limits can simply follow what's implied
> by the configuration. e.g. if high=100 max=80, just behave as if both
> high and max are 80.
> > 2. Comparing parent's and child's limits and saying that either can be
> > ignored because one is higher than the other isn't correct. A
> > parent's limit doesn't apply to each child separately. It has to
> > be aggregated. e.g. you can ignore a parent's setting if the sum
> > of all children's limits is smaller than the parent's but then
> > again there could still be a lower limit higher up the tree, so
> > they would still have to be examined.
> This part still seems weird tho. What am I misunderstanding?

You are right, the checks are unncessary. I'll delete them.