Re: [PATCH RESEND v6 4/8] blk-throttle: fix io hung due to config updates

[Yu Kuai]

Hi

在 2022/07/28 17:33, Michal Koutný 写道:
> On Wed, Jul 27, 2022 at 08:39:19AM -1000, Tejun Heo <tj@xxxxxxxxxx> wrote:
> > I'm not quiet sure this is correct. What if the limit keeps changing across
> > different values? Then we'd be calculating the skipped amount based on the
> > last configuration only which would be incorrect.
>
> When one change of configuration is correct, then all changes must be
> correct by induction. It's sufficient to take into account only the one
> old config and the new one.
>
> This __tg_update_skipped() calculates bytes_skipped with the limit
> before the change and bytes_skipped are used (divided by) the new limit
> in tg_with_in_bps_limit().
> The accumulation of bytes_skipped across multiple changes (until slice
> properly ends) is proportional to how bytes_allowed would grow over
> time.
> That's why I find this correct (I admit I had to look back into my
> notes when this was first discussed).
>
> HTH,
> Michal

Hi, Tejun

Michal already explain it very well, please let me know if you still
thinks there are better ways.

Thanks,
Kuai