Hi Jonathan, Thanks for the response.
On Tue, May 26, 2020 at 2:50 PM Jonathan Morton <[email protected]> wrote: > > On 26 May, 2020, at 12:47 pm, Jose Blanquicet <[email protected]> wrote: > > > > We have an embedded system with limited CPU resources that acts as > > gateway to provide Internet access from LTE to a private Wi-Fi > > network. Our problem is that the bandwidth on LTE and Wi-Fi links is > > higher than what the system is able to handle thus it reaches 100% of > > CPU load when we perform a simple speed test from a device connected > > to our Wi-Fi Hotspot. > > > > Therefore, we want to limit the bandwidth to avoid system gets > > saturated is such use-case. To do so, we thought to use the QDISC-TBF > > on the Wi-Fi interface. For instance, to have 10Mbps: > > > > tc qdisc add dev wlan0 root tbf rate 10mbit burst 12500b latency 50ms > > > > It worked correctly and maximum rate was limited to 10Mbps. However, > > we noticed that the CPU load added by the TBF was not negligible for > > our system. > > Just how limited is the CPU on this device? I have successfully shaped at > several tens of Mbps on a Pentium-MMX, where the limiting factor may have > been the PCI bus rather than the CPU itself. We have just a percentage of an ARM Cortex A7 (1.2GHz) because the rest is reserved for modem. We are now trying to optimize all the applications in the system but LTE<->WIFI data transfer is indeed the use-case that puts our system in crisis. > Assuming your CPU is of that order of capability, I would suggest installing > Cake using the out-of-tree build process, and the latest stable version of > the iproute2 tools to configure it. Start with: > > git clone https://github.com/dtaht/sch_cake.git > > This provides a more efficient and more effective shaper than TBF, and a more > effective AQM than a policer, and good flow-isolation properties, all in a > single bundle that will be more efficient than running two separate > components. > > Once installed, the following should set it up nicely for you: > > tc qdisc replace dev wlan0 root cake bandwidth 10Mbit besteffort > flows ack-filter > > Cake is considered quite a heavyweight solution, but very effective. If it > doesn't work well for this particular use case, it may be feasible to > backport some more recent work which takes a simpler approach, though along > similar lines. Interesting, we will have a look at this and do some test to see how it behaves in our "particular" environment. Thanks, Jose _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
