iflib: implement driver-provided queue selection for simple txHEADmain

Until now, simple tx has used its own queue selector, and has
ignored isc_txq_select and isc_txq_select_v2 (not this only
seems to matter for ice(4) with dcb enabled). This change
makes simple-tx use isc_txq_select* when present.

The implementation is defined to be efficient, with a
transmit routine chosen up-front that hard-codes the
queue selection and calls an always-inlined body.  This
avoids a useless test per packet in the hotpath, and
also may avoid speculation into header parsing.

Note that this was designed for readability and efficiency
in the common case (interface up, not ALTQ).  That's why
we do queue selection without duplicating nic-running and
altq checks, leaving them to the common implmentation.

Sponsored by: Netflix
Reviewed by: kbowling
Differential Revision: https://reviews.freebsd.org/D59712

0 files changed, 0 insertions, 0 deletions