On Wed, Mar 18, 2015 at 8:20 AM, Jonathan Morton wrote: > > > On 18 Mar, 2015, at 17:10, Kathleen Nichols wrote: > > > > How are you relating target delay to bandwidth? > > Essentially, I use 5ms as a minimum, and increase it if necessary to > accommodate a couple of MTU-sized packets at the shaping rate. This keeps > things nicely under control at low bandwidths, and I find that cake remains > useful and usable even at 64Kbps (without making even the usual adjustments > to host or link configuration for such low speeds). > In the cake2 (or maybe it was the unpublished cake3) version, I had a lighter weight version of the codel algorithm, that did not have a target parameter at all. Instead it just took the interval parameter and shifted it right 4 (yielding a target of 6.xms from an interval of 100ms) This saves on a memory access (and storage per queue!) , and I felt that any differences in behavior would be unnoticeable. And they were. This is also above the bound for cable-modem media access that greg white (rightly or wrongly) believed existed. So I have no problem in eliminating "target" entirely. Cake (without bandwidth shaping engaged) uses more cpu than fq_codel did and this was one of many optimizations I'd attempted (or successfully added). Cake with shaping is a bit less cpu than sqm-scripts htb + fq_codel + filters. It also looked like cake could be poured into gates, with a bit more research, and testing. > I can do this in cake because the shaping rate is known, whereas the pure > codel and fq_codel qdiscs do not have reliable link-speed information. As for this bit, we seemed to need to account for a MTU's worth of data at the lower speeds, and I did not explore what fiddling with the interval and auto-calc-ing the target did at these speeds, as yet. > - Jonathan Morton > > _______________________________________________ > Codel mailing list > Codel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/codel > -- Dave Täht Let's make wifi fast, less jittery and reliable again! https://plus.google.com/u/0/107942175615993706558/posts/TVX3o84jjmb