Sebastian Moeller <[email protected]> writes: > Hi Toke, > > > >> On May 2, 2018, at 17:30, Toke Høiland-Jørgensen <[email protected]> wrote: >> >> Sebastian Moeller <[email protected]> writes: >> >>>> On May 2, 2018, at 17:11, Toke Høiland-Jørgensen <[email protected]> wrote: >>>> >>>> + /* The last segment may be shorter; we ignore this, which means >>>> + * that we will over-estimate the size of the whole GSO segment >>>> + * by the difference in size. This is conservative, so we live >>>> + * with that to avoid the complexity of dealing with it. >>>> + */ >>>> + len = shinfo->gso_size + hdr_len; >>>> + } >>> >>> >>> Hi Toke, >>> >>> so I am on the fence with this one, as the extreme case is having a >>> super packet consisting out of 1 full-MTU packet plus a tiny leftover >>> in that case we pay a 50% bandwidth sacrifice which seems a bit high. >>> Nowm I have no real feling how likely this full MTU plus 64 byte >>> packet issue is in real life, but in the past I often saw maximum >>> packetsizes of around 3K bytes on my router indicating that having a >>> sup packet consisting just out of two segments might not be that rare. >>> So is there an easy way for me to measure the probability of seeing >>> that issue? >>> >>> I am all for sacrificing some bandwidth for better latency under load, >>> but few users will be happy with a 50% loss of bandwidth... >> >> Well, in most cases such GSO segments will be split anyway (we split if >> <= 1 Gbps). So this inaccuracy will only hit someone who enables the >> shaper *and sets it to a rate rate > 1Gbps*. Which is not a deployment >> mode we have seen a lot of, I think? > > Oh, I agree with that rationale; I was still under the impression that > we want to go back to a (configurable) serialization delay based > segmentation threshold and then this might become an issue (especially > on puny routers will profit from the reduced routing cost* of > GSO/GRO). Also I fear that 1Gbps service will become an issue rather > sooner than later, even though I would assume that then dual segment > super-packets should really be rare...
Sure, let's go back and revisit if and when we do that :) -Toke _______________________________________________ Cake mailing list [email protected] https://lists.bufferbloat.net/listinfo/cake
