Re: [PATCH V4 02/15] blk-throttle: add .high interface

From: Tejun Heo
Date: Wed Nov 23 2016 - 16:11:22 EST


On Tue, Nov 22, 2016 at 03:08:36PM -0800, Shaohua Li wrote:
> Yep, the limit could be high or max. It's doable moving the restrictions on
> input, but will increase trouble using the limits. If high is bigger than max,
> can I set high to max? if not, I'd prefer to keep the restrictions.

You can do that internally but userland should keep seeing what it

> > I haven't read the whole thing yet but this looks a bit suspicious. A
> > css going offline indicates that the destruction of the css started.
> > I don't get why that'd reset high limits. There can be a lot of async
> > IOs after offline.
> Ok. We do want to reset the limits. Because if no cgroup has high limit, we
> definitively should use max limit for all cgroups. The whole state machine
> (switching between high and max limit) is meaningless in that case.
> Is pd_free_fn a good place to guarantee anyc IOs finish?