[dpdk-dev] [PATCH] kni:optimization of rte_kni_rx_burst

[Olivier Deme]

Thank you Hemant, I think there might be one issue left with the patch 
though.
The alloc_q must initially be filled with mbufs before getting mbuf back 
on the tx_q.

So the patch should allow rte_kni_rx_burst to check if alloc_q is empty.
If so, it should invoke kni_allocate_mbufs(kni, 0)
(to fill the alloc_q with MAX_MBUF_BURST_NUM mbufs)

The patch for rte_kni_rx_burst would then look like:

@@ -575,7 +575,7 @@ rte_kni_rx_burst(struct rte_kni *kni, struct 
rte_mbuf **mbufs, unsigned num)

      /* If buffers removed, allocate mbufs and then put them into 
alloc_q */
      if (ret)
-        kni_allocate_mbufs(kni);
+      kni_allocate_mbufs(kni, ret);
+  else if (unlikely(kni->alloc_q->write == kni->alloc_q->read))
+      kni_allocate_mbufs(kni, 0);


Olivier.

On 25/02/15 11:48, Hemant Agrawal wrote:
> From: Hemant Agrawal <hemant at freescale.com>
>
> if any buffer is read from the tx_q, MAX_BURST buffers will be allocated and attempted to be added to to the alloc_q.
> This seems terribly inefficient and it also looks like the alloc_q will quickly fill to its maximum capacity. If the system buffers are low in number, it will reach "out of memory" situation.
>
> This patch allocates the number of buffers as many dequeued from tx_q.
>
> Signed-off-by: Hemant Agrawal <hemant at freescale.com>
> ---
>   lib/librte_kni/rte_kni.c | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/lib/librte_kni/rte_kni.c b/lib/librte_kni/rte_kni.c
> index 4e70fa0..4cf8e30 100644
> --- a/lib/librte_kni/rte_kni.c
> +++ b/lib/librte_kni/rte_kni.c
> @@ -128,7 +128,7 @@ struct rte_kni_memzone_pool {
>   
>   
>   static void kni_free_mbufs(struct rte_kni *kni);
> -static void kni_allocate_mbufs(struct rte_kni *kni);
> +static void kni_allocate_mbufs(struct rte_kni *kni, int num);
>   
>   static volatile int kni_fd = -1;
>   static struct rte_kni_memzone_pool kni_memzone_pool = {
> @@ -575,7 +575,7 @@ rte_kni_rx_burst(struct rte_kni *kni, struct rte_mbuf **mbufs, unsigned num)
>   
>   	/* If buffers removed, allocate mbufs and then put them into alloc_q */
>   	if (ret)
> -		kni_allocate_mbufs(kni);
> +		kni_allocate_mbufs(kni, ret);
>   
>   	return ret;
>   }
> @@ -594,7 +594,7 @@ kni_free_mbufs(struct rte_kni *kni)
>   }
>   
>   static void
> -kni_allocate_mbufs(struct rte_kni *kni)
> +kni_allocate_mbufs(struct rte_kni *kni, int num)
>   {
>   	int i, ret;
>   	struct rte_mbuf *pkts[MAX_MBUF_BURST_NUM];
> @@ -620,7 +620,10 @@ kni_allocate_mbufs(struct rte_kni *kni)
>   		return;
>   	}
>   
> -	for (i = 0; i < MAX_MBUF_BURST_NUM; i++) {
> +	if (num == 0 || num > MAX_MBUF_BURST_NUM)
> +		num = MAX_MBUF_BURST_NUM;
> +
> +	for (i = 0; i < num; i++) {
>   		pkts[i] = rte_pktmbuf_alloc(kni->pktmbuf_pool);
>   		if (unlikely(pkts[i] == NULL)) {
>   			/* Out of memory */
> @@ -636,7 +639,7 @@ kni_allocate_mbufs(struct rte_kni *kni)
>   	ret = kni_fifo_put(kni->alloc_q, (void **)pkts, i);
>   
>   	/* Check if any mbufs not put into alloc_q, and then free them */
> -	if (ret >= 0 && ret < i && ret < MAX_MBUF_BURST_NUM) {MAX_MBUF_BURST_NUM
>
> +	if (ret >= 0 && ret < i && ret < num) {
>   		int j;
>   
>   		for (j = ret; j < i; j++)

-- 
	*Olivier Demé*
*Druid Software Ltd.*
*Tel: +353 1 202 1831*
*Email: odeme at druidsoftware.com <mailto:odeme at druidsoftware.com>*
*URL: http://www.druidsoftware.com*
	*Hall 7, stand 7F70.*
Druid Software: Monetising enterprise small cells solutions.