From: Yunjian Wang <wangyunj...@huawei.com> In kni_allocate_mbufs(), we alloc mbuf for alloc_q as this code. allocq_free = (kni->alloc_q->read - kni->alloc_q->write - 1) \ & (MAX_MBUF_BURST_NUM - 1); The value of allocq_free maybe zero, for example : The ring size is 1024. After init, write = read = 0. Then we fill kni->alloc_q to full. At this time, write = 1023, read = 0.
Then the kernel send 32 packets to userspace. At this time, write = 1023, read = 32. And then the userspace receive this 32 packets. Then fill the kni->alloc_q, (32 - 1023 - 1) & 31 = 0, fill nothing. ... Then the kernel send 32 packets to userspace. At this time, write = 1023, read = 992. And then the userspace receive this 32 packets. Then fill the kni->alloc_q, (992 - 1023 - 1) & 31 = 0, fill nothing. Then the kernel send 32 packets to userspace. The kni->alloc_q only has 31 mbufs and will drop one packet. Absolutely, this is a special scene. Normally, it will fill some mbufs everytime, but may not enough for the kernel to use. In this patch, we always keep the kni->alloc_q to full for the kernel to use. Fixes: 49da4e82cf94 ("kni: allocate no more mbuf than empty slots in queue") Cc: sta...@dpdk.org Signed-off-by: Cheng Liu <liuchen...@huawei.com> Signed-off-by: Yunjian Wang <wangyunj...@huawei.com> Acked-by: Ferruh Yigit <ferruh.yi...@intel.com> --- v3: update patch title v2: add fixes tag and update commit log --- lib/kni/rte_kni.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/lib/kni/rte_kni.c b/lib/kni/rte_kni.c index 9dae6a8d7c..eb24b0d0ae 100644 --- a/lib/kni/rte_kni.c +++ b/lib/kni/rte_kni.c @@ -677,8 +677,9 @@ kni_allocate_mbufs(struct rte_kni *kni) return; } - allocq_free = (kni->alloc_q->read - kni->alloc_q->write - 1) - & (MAX_MBUF_BURST_NUM - 1); + allocq_free = kni_fifo_free_count(kni->alloc_q); + allocq_free = (allocq_free > MAX_MBUF_BURST_NUM) ? + MAX_MBUF_BURST_NUM : allocq_free; for (i = 0; i < allocq_free; i++) { pkts[i] = rte_pktmbuf_alloc(kni->pktmbuf_pool); if (unlikely(pkts[i] == NULL)) { -- 2.23.0