svn commit: r273112 - head/sys/dev/ixgbe

[Adrian Chadd]

On 6 November 2014 09:58, Ryan Stone <rysto32 at gmail.com> wrote:
> On Thu, Nov 6, 2014 at 12:21 PM, Adrian Chadd <adrian at freebsd.org> wrote:
>> Hm, are there any other hardware counters that we can use to see what
>> was dropped?
>
> On the 82599 and later you need to configure the RQSMR register to map
> queue pools to indices and then the QPRDC[i] register will contain the
> number of drops.

Ok.

> Note that the 82598 doesn't support the DROPEN bit in the SRRCTL
> register.  There is a separate DROPEN register on the 82598, but I
> have the following worrisome comment in my version of ixgbe:
>
>     if (hw->mac.type == ixgbe_mac_82598EB) {
>         /*
>          * The DROPEN register is intended to allow us to immediately
>          * drop packets that cannot be DMA'ed to memory right away to
>          * avoid head-of-line blocking.  However we have observed that
>          * enabling this functionality can lead to situations where a
>          * queue will drop every packet destined for it silently, so
>          * we instead accept the HOL blocking and disable the immediate
>          * dropping
>          */
>         IXGBE_WRITE_REG(&adapter->hw, IXGBE_DROPEN, 0);

... even if there's ring slots?



-adrian