Hi Tomasz,

-----Original Message-----
From: Kulasek, TomaszX
Sent: Tuesday, February 02, 2016 10:01 AM
To: Ananyev, Konstantin; dev@dpdk.org
Subject: RE: [dpdk-dev] [PATCH 1/2] ethdev: add buffered tx api

Hi Konstantin,

quoted

-----Original Message-----
From: Ananyev, Konstantin
Sent: Friday, January 15, 2016 19:45
To: Kulasek, TomaszX; dev@dpdk.org
Subject: RE: [dpdk-dev] [PATCH 1/2] ethdev: add buffered tx api

Hi Tomasz,

quoted

+		/* get new buffer space first, but keep old space around */
+		new_bufs = rte_zmalloc("ethdev->txq_bufs",
+				sizeof(*dev->data->txq_bufs) * nb_queues, 0);
+		if (new_bufs == NULL)
+			return -(ENOMEM);
+

Why not to allocate space for txq_bufs together with tx_queues (as one
chunk for both)?
As I understand there is always one to one mapping between them anyway.
Would simplify things a bit.
Or even introduce a new struct to group with all related tx queue info
togetehr struct rte_eth_txq_data {
	void *queue; /*actual pmd  queue*/
	struct rte_eth_dev_tx_buffer buf;
	uint8_t state;
}
And use it inside struct rte_eth_dev_data?
Would probably give a better data locality.

Introducing such a struct will require a huge rework of pmd drivers. I don't think it's worth only for this one feature.

Why not?
Things are getting more and more messy here: now we have a separate array of pointer to queues,
Separate array of queue states, you are going to add separate array of tx buffers.
For me it seems logical to unite all these 3 fields into one sub-struct. 

quoted

quoted

+/**
+ * @internal
+ * Structure used to buffer packets for future TX
+ * Used by APIs rte_eth_tx_buffer and rte_eth_tx_buffer_flush  */
+struct rte_eth_dev_tx_buffer {
+	struct rte_mbuf *pkts[RTE_ETHDEV_TX_BUFSIZE];

I think it is better to make size of pkts[] configurable at runtime.
There are a lot of different usage scenarios - hard to predict what would
be an optimal buffer size for all cases.

This buffer is allocated in eth_dev shared memory, so there are two scenarios:
1) We have prealocated buffer with maximal size, and then we can set threshold level without restarting device, or
2) We need to set its size before starting device.

Second one is better, I think.

Yep, I was thinking about 2) too.
Might be an extra parameter in struct rte_eth_txconf.

Tomasz