RE: [PATCH 04/14] bna: Add Multiple Tx Queue Support

From: Ben Hutchings [mailto:bhutchings@solarflare.com]
Sent: Tuesday, August 16, 2011 2:49 PM

On Tue, 2011-08-16 at 14:19 -0700, Rasesh Mody wrote:

quoted

Change details:
 - Add macros bna_prio_allow, bna_default_nw_prio, bna_iscsi_prio,
   bna_is_iscsi_over_cee
 - Added support for multipe Tx queues with a separate iSCSI Tx queue

based

quoted

   on the default value of iSCSI port number. The feature is supported

based

quoted

   on the underlying hardware and enabled for DCB (CEE) mode only.
 - Allocate multiple TxQ resource in netdev
 - Implement bnad_tx_select_queue() which enables the correct

selection of

quoted

   TxQ Id (and tcb). This function is called either by the kernel to

channel

quoted

   packets to the right TxQ
 - bnad_tx_select_queue() returns priority, while only a few packets

during

quoted

   transition could have wrong priority, all will be associated with a

valid

quoted

   non-NULL tcb.
 - Implement bnad_iscsi_tcb_get() and BNAD_IS_ISCSI_PKT() for iSCSI

packet

quoted

   inspection and retrieval of tcb corresponding to the iSCSI

priority.

quoted

 - Construction of priority indirection table to be used by bnad to

direct

quoted

   packets into TxQs

[...]

You probably should implement TX priority classes through the
ndo_setup_tc operation, not ndo_select_queue.

The reason we went with ndo_select_queue is due to the need for mapping
iSCSI packets (TCP port 3260) to a priority derived from DCB configuration.
Here the iSCSI packets may not have any tc defined in the packet header. 
Thanks,
Rasesh