[v2] kni: fix wrong mbuf alloc count in kni_allocate_mbufs
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Commit Message
From: Yunjian Wang <wangyunjian@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: stable@dpdk.org
Signed-off-by: Cheng Liu <liucheng11@huawei.com>
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
---
v2:
add fixes tag and update commit log
---
lib/kni/rte_kni.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
Comments
On 6/22/2021 11:57 AM, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@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: stable@dpdk.org
>
> Signed-off-by: Cheng Liu <liucheng11@huawei.com>
> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
What do you think to change patch title to something like:
kni: fix mbuf allocation for alloc FIFO
> -----Original Message-----
> From: Ferruh Yigit [mailto:ferruh.yigit@intel.com]
> Sent: Tuesday, June 22, 2021 8:28 PM
> To: wangyunjian <wangyunjian@huawei.com>; dev@dpdk.org
> Cc: thomas@monjalon.net; gowrishankar.m@linux.vnet.ibm.com;
> dingxiaoxiong <dingxiaoxiong@huawei.com>; stable@dpdk.org; liucheng (J)
> <liucheng11@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 <wangyunjian@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: stable@dpdk.org
> >
> > Signed-off-by: Cheng Liu <liucheng11@huawei.com>
> > Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
>
> Acked-by: Ferruh Yigit <ferruh.yigit@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
@@ -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)) {