Re: [Xen-devel] [PATCH 03/24] xen: credit1: return the 'time remaining to the limit' as next timeslice.

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 17/08/16 18:17, Dario Faggioli wrote:
> If vcpu x has run for 200us, and sched_ratelimit_us is
> 1000us, continue running x _but_ return 1000us-200us as
> the next time slice. This way, next scheduling point will
> happen in 800us, i.e., exactly at the point when x crosses
> the threshold, and can be descheduled (if appropriate).
> 
> Right now (without this patch), we're always returning
> sched_ratelimit_us (1000us, in the example above), which
> means we're (potentially) allowing x to run more than
> it should have been able to (even when considering rate
> limiting into account).

Part of the reason I went with this in the first place was because I
wanted to avoid really short timers.  Part of the reason for the
ratelimit was actually to limit the amount of time spent in the
scheduler.  Since we expect ratelimit to normally be pretty short,
waiting for the whole ratelimit time seemed like a good idea.

Thoughts?

 -George


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