From: Olivier Deme <odeme@druidsoftware.com>
To: "Hemant@freescale.com" <Hemant@freescale.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] kni:optimization of rte_kni_rx_burst
Date: Wed, 25 Feb 2015 12:28:53 +0000 [thread overview]
Message-ID: <54EDC005.10008@druidsoftware.com> (raw)
In-Reply-To: <BY2PR0301MB069369AA0C7436E5F9A63AE9C2170@BY2PR0301MB0693.namprd03.prod.outlook.com>
I guess it would be unusual but possible for the kernel to enqueue
faster to tx_q than the application dequeues.
But that would also be possible with a real NIC, so I think it is
acceptable for the kernel to have to drop egress packets in that case.
On 25/02/15 12:24, Hemant@freescale.com wrote:
> Hi OIivier
> Comments inline.
> Regards,
> Hemant
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Olivier Deme
>> Sent: 25/Feb/2015 5:44 PM
>> To: dev@dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH] kni:optimization of rte_kni_rx_burst
>>
>> Thank you Hemant, I think there might be one issue left with the patch though.
>> The alloc_q must initially be filled with mbufs before getting mbuf back on the
>> tx_q.
>>
>> So the patch should allow rte_kni_rx_burst to check if alloc_q is empty.
>> If so, it should invoke kni_allocate_mbufs(kni, 0) (to fill the alloc_q with
>> MAX_MBUF_BURST_NUM mbufs)
>>
>> The patch for rte_kni_rx_burst would then look like:
>>
>> @@ -575,7 +575,7 @@ rte_kni_rx_burst(struct rte_kni *kni, struct rte_mbuf
>> **mbufs, unsigned num)
>>
>> /* If buffers removed, allocate mbufs and then put them into alloc_q */
>> if (ret)
>> - kni_allocate_mbufs(kni);
>> + kni_allocate_mbufs(kni, ret);
>> + else if (unlikely(kni->alloc_q->write == kni->alloc_q->read))
>> + kni_allocate_mbufs(kni, 0);
>>
> [hemant] This will introduce a run-time check.
>
> I missed to include the other change in the patch.
> I am doing it in kni_alloc i.e. initiate the alloc_q with default burst size.
> kni_allocate_mbufs(ctx, 0);
>
> In a way, we are now suggesting to reduce the size of alloc_q to only default burst size.
>
> Can we reach is situation, when the kernel is adding packets faster in tx_q than the application is able to dequeue?
> alloc_q can be empty in this case and kernel will be striving.
>
>> Olivier.
>>
>> On 25/02/15 11:48, Hemant Agrawal wrote:
>>> From: Hemant Agrawal <hemant@freescale.com>
>>>
>>> if any buffer is read from the tx_q, MAX_BURST buffers will be allocated and
>> attempted to be added to to the alloc_q.
>>> This seems terribly inefficient and it also looks like the alloc_q will quickly fill
>> to its maximum capacity. If the system buffers are low in number, it will reach
>> "out of memory" situation.
>>> This patch allocates the number of buffers as many dequeued from tx_q.
>>>
>>> Signed-off-by: Hemant Agrawal <hemant@freescale.com>
>>> ---
>>> lib/librte_kni/rte_kni.c | 13 ++++++++-----
>>> 1 file changed, 8 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/lib/librte_kni/rte_kni.c b/lib/librte_kni/rte_kni.c index
>>> 4e70fa0..4cf8e30 100644
>>> --- a/lib/librte_kni/rte_kni.c
>>> +++ b/lib/librte_kni/rte_kni.c
>>> @@ -128,7 +128,7 @@ struct rte_kni_memzone_pool {
>>>
>>>
>>> static void kni_free_mbufs(struct rte_kni *kni); -static void
>>> kni_allocate_mbufs(struct rte_kni *kni);
>>> +static void kni_allocate_mbufs(struct rte_kni *kni, int num);
>>>
>>> static volatile int kni_fd = -1;
>>> static struct rte_kni_memzone_pool kni_memzone_pool = { @@ -575,7
>>> +575,7 @@ rte_kni_rx_burst(struct rte_kni *kni, struct rte_mbuf
>>> **mbufs, unsigned num)
>>>
>>> /* If buffers removed, allocate mbufs and then put them into alloc_q
>> */
>>> if (ret)
>>> - kni_allocate_mbufs(kni);
>>> + kni_allocate_mbufs(kni, ret);
>>>
>>> return ret;
>>> }
>>> @@ -594,7 +594,7 @@ kni_free_mbufs(struct rte_kni *kni)
>>> }
>>>
>>> static void
>>> -kni_allocate_mbufs(struct rte_kni *kni)
>>> +kni_allocate_mbufs(struct rte_kni *kni, int num)
>>> {
>>> int i, ret;
>>> struct rte_mbuf *pkts[MAX_MBUF_BURST_NUM]; @@ -620,7 +620,10
>> @@
>>> kni_allocate_mbufs(struct rte_kni *kni)
>>> return;
>>> }
>>>
>>> - for (i = 0; i < MAX_MBUF_BURST_NUM; i++) {
>>> + if (num == 0 || num > MAX_MBUF_BURST_NUM)
>>> + num = MAX_MBUF_BURST_NUM;
>>> +
>>> + for (i = 0; i < num; i++) {
>>> pkts[i] = rte_pktmbuf_alloc(kni->pktmbuf_pool);
>>> if (unlikely(pkts[i] == NULL)) {
>>> /* Out of memory */
>>> @@ -636,7 +639,7 @@ kni_allocate_mbufs(struct rte_kni *kni)
>>> ret = kni_fifo_put(kni->alloc_q, (void **)pkts, i);
>>>
>>> /* Check if any mbufs not put into alloc_q, and then free them */
>>> - if (ret >= 0 && ret < i && ret < MAX_MBUF_BURST_NUM)
>> {MAX_MBUF_BURST_NUM
>>> + if (ret >= 0 && ret < i && ret < num) {
>>> int j;
>>>
>>> for (j = ret; j < i; j++)
>> --
>> *Olivier Demé*
>> *Druid Software Ltd.*
>> *Tel: +353 1 202 1831*
>> *Email: odeme@druidsoftware.com <mailto:odeme@druidsoftware.com>*
>> *URL: http://www.druidsoftware.com*
>> *Hall 7, stand 7F70.*
>> Druid Software: Monetising enterprise small cells solutions.
--
*Olivier Demé*
*Druid Software Ltd.*
*Tel: +353 1 202 1831*
*Email: odeme@druidsoftware.com <mailto:odeme@druidsoftware.com>*
*URL: http://www.druidsoftware.com*
*Hall 7, stand 7F70.*
Druid Software: Monetising enterprise small cells solutions.
next prev parent reply other threads:[~2015-02-25 12:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-25 11:48 Hemant Agrawal
2015-02-25 12:13 ` Olivier Deme
2015-02-25 12:24 ` Hemant
2015-02-25 12:28 ` Olivier Deme [this message]
2015-02-25 12:38 ` Marc Sune
2015-02-25 12:51 ` Olivier Deme
2015-02-25 13:29 ` Jay Rolette
2015-02-26 7:00 ` Hemant
2015-02-26 12:56 ` Marc Sune
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