kni: fix possible alloc_q starvation when mbufs are exhausted
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Commit Message
In some scenarios, mbufs returned by rte_kni_rx_burst are not freed
immediately. So kni_allocate_mbufs may be failed, but we don't know.
Even worse, when alloc_q is completely exhausted, kni_net_tx in
rte_kni.ko will drop all tx packets. kni_allocate_mbufs is never
called again, even if the mbufs are eventually freed.
In this patch, we always try to allocate mbufs for alloc_q.
Don't worry about alloc_q being allocated too many mbufs, in fact,
the old logic will gradually fill up alloc_q.
Also, the cost of more calls to kni_allocate_mbufs should be acceptable.
Fixes: 3e12a98fe397 ("kni: optimize Rx burst")
Cc: Hemant@freescale.com
Cc: stable@dpdk.org
Signed-off-by: Yangchao Zhou <zhouyates@gmail.com>
---
lib/kni/rte_kni.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
@@ -634,9 +634,9 @@ rte_kni_rx_burst(struct rte_kni *kni, struct rte_mbuf **mbufs, unsigned int num)
{
unsigned int ret = kni_fifo_get(kni->tx_q, (void **)mbufs, num);
- /* If buffers removed, allocate mbufs and then put them into alloc_q */
- if (ret)
- kni_allocate_mbufs(kni);
+ /* Always try to allocate mbufs for alloc_q to avoid starvation when
+ * kni->pktmbuf_pool is exhausted. */
+ kni_allocate_mbufs(kni);
return ret;
}