What does adapter->stats.mpc[] report for ixgbe?

[Jack Vogel]

Juli is correct, the FIFO is not partitioned by the driver queues as they
exist in the current driver, its only seperated into the 3 parts I
mentioned.

Jack


On Mon, May 7, 2012 at 9:55 PM, Juli Mallett <jmallett at freebsd.org> wrote:

> On Mon, May 7, 2012 at 9:42 PM, Vijay Singh <vijju.singh at 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.)
>