On 3/27/19 7:30 PM, Stephen Hemminger wrote: >> on CAN networking hardware we (the CAN community) experience a lot silent, >> unwanted frame drops inside the kernel. (See first patch for details.) So >> here's a patch series to keep pfifo_fast as default scheduler for CAN hardware >> by default. > > Why do you set fq_codel as default qdisc if you know it doesn't work right for your > environment. Is this a distro's want one value problem? This is a many fold problem. - Consider a random Linux developer attaching one of the mainline supported USB-CAN adapters to his/her development laptop and doing some random CAN test. As far a I heard all modern Linux distributions (but not debian) enable fq_codel per kernel .config or via systemd. The user will experiences dropped CAN frames on the first 1000 packages. This is not a good user experience. - From the user space point of view the sysctl net.core.default_qdisc behaves a bit strange. Why can I enable a queuing discipline by default that's known not to work on CAN devices. You might think the kernel (should) know that CAN devices best work with pfifo_fast (or not NET_SCHED at all). - Addressing your question directly: Mixed environment. fq_codel works great on Ethernet, but terrible on CAN. Of course I an use "tc" to configure the way I want to. But from my point of view it would be nice, if the kernel uses sane default...and handles the net.core.default_qdisc default in a sane way. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
Attachment:
signature.asc
Description: OpenPGP digital signature
