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

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Date:	Tue, 16 Aug 2011 16:32:20 -0700
From:	Rasesh Mody <rmody@...cade.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Adapter Linux Open SRC Team 
	<adapter_linux_open_src_team@...cade.COM>,
	Gurunatha Karaje <gkaraje@...cade.com>
Subject: RE: [PATCH 04/14] bna: Add Multiple Tx Queue Support

>From: Ben Hutchings [mailto:bhutchings@...arflare.com]
>Sent: Tuesday, August 16, 2011 2:49 PM
>
>On Tue, 2011-08-16 at 14:19 -0700, Rasesh Mody wrote:
>> 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
>>    on the default value of iSCSI port number. The feature is supported
>based
>>    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
>>    TxQ Id (and tcb). This function is called either by the kernel to
>channel
>>    packets to the right TxQ
>>  - bnad_tx_select_queue() returns priority, while only a few packets
>during
>>    transition could have wrong priority, all will be associated with a
>valid
>>    non-NULL tcb.
>>  - Implement bnad_iscsi_tcb_get() and BNAD_IS_ISCSI_PKT() for iSCSI
>packet
>>    inspection and retrieval of tcb corresponding to the iSCSI
>priority.
>>  - Construction of priority indirection table to be used by bnad to
>direct
>>    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