From: wangyunjian <wangyunjian@huawei.com>
To: Thomas Monjalon <thomas@monjalon.net>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"stable@dpdk.org" <stable@dpdk.org>,
"ferruh.yigit@intel.com" <ferruh.yigit@intel.com>,
"gowrishankar.m@linux.vnet.ibm.com"
<gowrishankar.m@linux.vnet.ibm.com>,
dingxiaoxiong <dingxiaoxiong@huawei.com>,
"liucheng (J)" <liucheng11@huawei.com>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v3] kni: fix mbuf allocation for alloc FIFO
Date: Wed, 23 Jun 2021 12:16:05 +0000 [thread overview]
Message-ID: <aa1afe7f17e74f0da8bca632c8ad6226@huawei.com> (raw)
In-Reply-To: <3564511.TeOt0uO2Lr@thomas>
> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas@monjalon.net]
> Sent: Wednesday, June 23, 2021 4:46 AM
> To: wangyunjian <wangyunjian@huawei.com>; liucheng (J)
> <liucheng11@huawei.com>
> Cc: dev@dpdk.org; stable@dpdk.org; ferruh.yigit@intel.com;
> gowrishankar.m@linux.vnet.ibm.com; dingxiaoxiong
> <dingxiaoxiong@huawei.com>; wangyunjian <wangyunjian@huawei.com>
> Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v3] kni: fix mbuf allocation for alloc
> FIFO
>
> 22/06/2021 14:44, wangyunjian:
> > 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>
> > ---
> > 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);
>
> Can we insert a comment here to explain the logic?
OK, how about like this?
/* Because 'read/write' maybe not volatile, so use kni_fifo_free_count()
* to get the num of available elements in the fifo
*/
>
> > + 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)) {
>
> About the title, I don't understand the part "for alloc FIFO", given all mbufs are
> in a FIFO queue in KNI, right?
The title is "kni: fix mbuf allocation for FIFO queue"?
next prev parent reply other threads:[~2021-06-23 12:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4ebfe0d38b335a437edc9c58368153d005f562ce.1622460655.git.wangyunjian@huawei.com>
2021-06-22 10:57 ` [dpdk-stable] [PATCH v2] kni: fix wrong mbuf alloc count in kni_allocate_mbufs wangyunjian
2021-06-22 12:27 ` Ferruh Yigit
2021-06-22 12:32 ` wangyunjian
2021-06-22 12:44 ` [dpdk-stable] [dpdk-dev] [PATCH v3] kni: fix mbuf allocation for alloc FIFO wangyunjian
2021-06-22 20:46 ` Thomas Monjalon
2021-06-23 12:16 ` wangyunjian [this message]
2021-06-23 14:11 ` Ferruh Yigit
2021-06-23 14:41 ` Thomas Monjalon
2021-06-24 1:55 ` Ajit Khaparde
2021-06-24 7:43 ` Thomas Monjalon
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