From: Ilya Matveychikov <matvejchikov@gmail.com>
To: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] A question about (poor) rte_ethdev internal rx/tx callbacks design
Date: Mon, 13 Nov 2017 14:56:23 +0400 [thread overview]
Message-ID: <5F2502C3-99CF-4BE1-9DEC-364C5E636061@gmail.com> (raw)
In-Reply-To: <20171113103927.GP24849@6wind.com>
> On Nov 13, 2017, at 2:39 PM, Adrien Mazarguil <adrien.mazarguil@6wind.com> wrote:
>
> On Sat, Nov 11, 2017 at 09:18:45PM +0400, Ilya Matveychikov wrote:
>> Folks,
>>
>> Are you serious with it:
>>
>> typedef uint16_t (*eth_rx_burst_t)(void *rxq,
>> struct rte_mbuf **rx_pkts,
>> uint16_t nb_pkts);
>> typedef uint16_t (*eth_tx_burst_t)(void *txq,
>> struct rte_mbuf **tx_pkts,
>> uint16_t nb_pkts);
>>
>> I’m not surprised that every PMD stores port_id in every and each queue as having just the queue as an argument doesn’t allow to get the device. So the question is - why not to use something like:
>>
>> typedef uint16_t (*eth_rx_burst_t)(void *dev, uint16_t queue_id,
>> struct rte_mbuf **rx_pkts,
>> uint16_t nb_pkts);
>> typedef uint16_t (*eth_tx_burst_t)(void *dev, uint16_t queue_id,
>> struct rte_mbuf **tx_pkts,
>> uint16_t nb_pkts);
>
> I assume it's since the rte_eth_[rt]x_burst() wrappers already pay the price
> for that indirection, doing it twice would be redundant.
No need to do it twice, agree. We can pass dev pointer as well as queue, not just the queue’s
index.
>
> Basically the cost of storing a back-pointer to dev or a queue index in each
> Rx/Tx queue structure is minor compared to saving a couple of CPU cycles
> wherever we can.
Not sure about it. More data to store - more cache space to occupy. Note that every queue has
at least 4 bytes more than it actually needs. And RTE_MAX_QUEUES_PER_PORT is defined
by it’s default to 1024. So we may have 4k extra for each port....
>
> I'm not saying its the only solution nor the right approach, it's only one
> possible explanation for this API.
Thank you for your try.
next prev parent reply other threads:[~2017-11-13 10:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-11 17:18 Ilya Matveychikov
2017-11-12 2:43 ` Thomas Monjalon
2017-11-13 10:39 ` Adrien Mazarguil
2017-11-13 10:56 ` Ilya Matveychikov [this message]
2017-11-13 17:15 ` Adrien Mazarguil
2017-11-13 19:33 ` Ilya Matveychikov
2017-11-14 6:24 ` Andrew Rybchenko
2017-11-13 10:58 ` Ananyev, Konstantin
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