From: Vincent Jardin [mailto:vincent.jardin@6wind.com]
Sent: Wednesday, October 26, 2016 7:37 PM
Le 26 octobre 2016 2:11:26 PM "Van Haaren, Harry"
[off-list ref] a écrit :

quoted

quoted

-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jerin Jacob

So far, I have received constructive feedback from Intel, NXP and Linaro folks.
Let me know, if anyone else interested in contributing to the definition of
eventdev?

If there are no major issues in proposed spec, then Cavium would like work on
implementing and up-streaming the common code(lib/librte_eventdev/) and
an associated HW driver.(Requested minor changes of v2 will be addressed
in next version).

Hi All,

I will propose a minor change to the rte_event struct, allowing some bits
to be implementation specific. Currently the rte_event struct has no space
to allow an implementation store any metadata about the event. For software
performance it would be really helpful if there are some bits available for
the implementation to keep some flags about each event.

I suggest to rework the struct as below which opens 6 bits that were
otherwise wasted, and define them as implementation specific. By
implementation specific it is understood that the implementation can
overwrite any information stored in those bits, and the application must
not expect the data to remain after the event is scheduled.

OLD:
struct rte_event {
	uint32_t flow_id:24;
	uint32_t queue_id:8;
	uint8_t  sched_type; /* Note only 2 bits of 8 are required */

NEW:
struct rte_event {
	uint32_t flow_id:24;
	uint32_t sched_type:2; /* reduced size : but 2 bits is enough for the
enqueue types Ordered,Atomic,Parallel.*/
	uint32_t implementation:6; /* available for implementation specific
metadata */
	uint8_t queue_id; /* still 8 bits as before */

Bitfileds are efficients on Octeon. What's about other CPUs you have in
mind? x86 is not as efficient.

Given the rte_event struct is 16 bytes and there's no free space to use, I see no alternative than using bitfields in this case. Wecloming suggestions of a better way to layout the structure to avoid the bitfield.

Regards, -Harry