On Tue, 2015-07-28 at 07:31 -0700, Simon Barber wrote: > The issue is that Codel tries to keep the delay low, and will start > dropping when sojourn time grows above 5ms for 100ms. For longer RTT links > more delay is necessary to avoid underutilizing the link. This is due to > the multiplicative decrease - it's worst with Reno, where the halving of > cWind means that you need to have a full BDP of data in the buffer to avoid > the link going idle when cWind is halved. With longer RTTs this means more > delay than Codel allows is required to avoid a throughput hit. The worst > case happens when a single flow is controlled, but that can be a common > situation. My proposal is to sense and have the target value in Codel > automatically adjust when this worst case scenario happens - which would > mitigate most of the downside.
As I said, I've never seen what you describe. 100ms value is not a go/nogo threshold. It is a hint, based on real world values. We are speaking of 100 ms sojourn time in the CoDel queue, not sojourn time in the Internet ! You can still have flows with 500 ms or even 10 sec rtt and codel just works fine. Are you sure you understood how this was working ? _______________________________________________ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat