> -----Original Message----- > From: Ferruh Yigit [mailto:ferruh.yi...@intel.com] > Sent: Friday, June 18, 2021 9:37 PM > To: wangyunjian <wangyunj...@huawei.com>; dev@dpdk.org > Cc: liucheng (J) <liuchen...@huawei.com>; dingxiaoxiong > <dingxiaoxi...@huawei.com> > Subject: Re: [dpdk-dev] [PATCH] kni: fix wrong mbuf alloc count in > kni_allocate_mbufs > > On 5/31/2021 1:09 PM, wangyunjian wrote: > > 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 (e.g 32 & (32 - 1) = 0), and it > > will not fill the alloc_q. When the alloc_q's free count is zero, it > > will drop the packet in kernel kni. > > > > nack > > Both 'read' & 'write' pointers can be max 'len-1', so 'read - write - 1' > can't be > 'len'. > For above example first part can't be '32'. > > But if you are observing a problem, can you please describe it a little more, > it > may be because of something else.
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 recieve 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 recieve 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. Thanks > > > In this patch, we set the allocq_free as the min between > > MAX_MBUF_BURST_NUM and the free count of the alloc_q. > > > > Signed-off-by: Cheng Liu <liuchen...@huawei.com> > > Signed-off-by: Yunjian Wang <wangyunj...@huawei.com> > > --- > > 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..20d8f20cef 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)) { > >