On Mon, May 7, 2012 at 9:42 PM, Vijay Singh <vijju.si...@gmail.com> wrote: >> normal net traffic. But for now in FreeBSD its just one which is divided >> into 3 parts: TX, RX, and FDIR (flow director). > > Jack, does the sw driver control in any way the partitioning of the > FIFO? I guess enabling 2 hw queues splits the FIFO in half. But > otherwise does the driver control this in any way?
I don't believe that multiple queues splits the FIFO (Jack can correct me if I'm wrong.) This is a small (very small) chunk of low-latency memory on the NIC itself that is used to store the packets as they come in off the wire before they are moved to a receive descriptor. The driver does have a way of partitioning the space between transmit and receive, look for "PBA" in the drivers. In some cases if you're doing mostly-transmit or mostly-receive it can be very helpful to tweak these values, but in the case where you're running out of receive FIFO space constantly, it's (in my limited experience) more likely to be a problem with bandwidth or latency between the NIC and main memory, causing backpressure within the NIC as it tries to move packets to receive buffers (which are the ones allocated in main, i.e. host, memory.) _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
