> -----Original Message----- > From: Ferruh Yigit [mailto:ferruh.yi...@intel.com] > Sent: Tuesday, June 22, 2021 8:28 PM > To: wangyunjian <wangyunj...@huawei.com>; dev@dpdk.org > Cc: tho...@monjalon.net; gowrishanka...@linux.vnet.ibm.com; > dingxiaoxiong <dingxiaoxi...@huawei.com>; sta...@dpdk.org; liucheng (J) > <liuchen...@huawei.com> > Subject: Re: [PATCH v2] kni: fix wrong mbuf alloc count in kni_allocate_mbufs > > On 6/22/2021 11:57 AM, 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, 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> > > What do you think to change patch title to something like: > kni: fix mbuf allocation for alloc FIFO
OK, I will change patch title later. Thanks