On 16 Mar, 2011, at 3:02 am, Dave Täht wrote: >>>> 1) Wired devices, where we want to push more 10+ Gbps, so we can assume >>>> a posted skb is transmitted immediately. Even a basic qdisc can be a >>>> performance bottleneck. Set TX ring size to 256 or 1024+ buffers to >>>> avoid taking too many interrupts. >>> >>> To talk to this a bit, the huge dynamic range discrepancy between a >>> 10GigE device and what it may be connected to worries me. Some form of >>> fair queuing should be applied before the data hits the driver. >> >> You mean plugging a 10GigE card into a 10Base-T hub? :-D > > More like 10GigE into a 1Gig switch. Or spewing out the entire contents > of a stream to one destination across the internet.
Then that's no different to what I have in my apartment right now - a GigE switch connected to a 100base-TX switch, then to a 2Mbps DSL uplink, which could then be routed (after bouncing around backhauls for a bit) through a 500Kbps 3G downlink to a computer I've isolated from the LAN. If the flow is responsive, as with every sane TCP, the queue will end up in front of the slowest link - at the 3G tower. That's where the AQM would need to be. The GigE adapter in my nettop would be largely idle, as a normal function of the TCP congestion window. If it isn't, the queue will build up at *every* narrowing of the channel and the packet loss will be astronomical. All AQM could do then is to pick any real traffic out of the din. - Jonathan _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
