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From: "Zhao1, Wei" <wei.zhao1@intel.com>
To: Morten Brørup <mb@smartsharesystems.com>, "Guo, Jia" <jia.guo@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	Thomas Monjalon <thomas@monjalon.net>,
	"Yigit, Ferruh" <ferruh.yigit@intel.com>,
	Andrew Rybchenko <arybchenko@solarflare.com>
Subject: Re: [dpdk-dev] ixgbe vector rx does not conform to rte_eth_rx_burst() API
Date: Thu, 16 Jul 2020 08:49:50 +0000
Message-ID: <MWHPR11MB1391060094945333DE8AC929B77F0@MWHPR11MB1391.namprd11.prod.outlook.com> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35C61127@smartserver.smartshare.dk>


> -----Original Message-----
> From: Morten Brørup <mb@smartsharesystems.com>
> Sent: Thursday, July 16, 2020 12:03 AM
> To: Zhao1, Wei <wei.zhao1@intel.com>; Guo, Jia <jia.guo@intel.com>
> Cc: dev@dpdk.org; Thomas Monjalon <thomas@monjalon.net>; Yigit, Ferruh
> <ferruh.yigit@intel.com>; Andrew Rybchenko <arybchenko@solarflare.com>
> Subject: ixgbe vector rx does not conform to rte_eth_rx_burst() API
> Wei, Jeff,
> For the ixgbe driver using vector functions, i.e. ixgbe_recv_pkts_vec(), calling
> rte_eth_rx_burst() with nb_pkts > RTE_IXGBE_MAX_RX_BURST only returns
> RTE_IXGBE_MAX_RX_BURST packets. E.g. calling rte_eth_rx_burst() with
> nb_pkts=64 only returns 32 packets.
> The API description of rte_eth_rx_burst() says:
> <quote>
> The rte_eth_rx_burst() function returns the number of packets actually
> retrieved, which is the number of rte_mbuf data structures effectively supplied
> into the rx_pkts array. A return value equal to nb_pkts indicates that the RX
> queue contained at least rx_pkts packets, and this is likely to signify that other
> received packets remain in the input queue. Applications implementing a
> "retrieve as much received packets as possible" policy can check this specific
> case and keep invoking the rte_eth_rx_burst() function until a value less than
> nb_pkts is returned.
> </quote>
> The driver implementation does not conform to the documented behavior for
> "retrieve as much received packets as possible" applications.

It seems not an issue, this function has comment bellow, it is design work in that way.

 * vPMD receive routine, only accept(nb_pkts >= RTE_IXGBE_DESCS_PER_LOOP)
 * Notice:
 * - nb_pkts < RTE_IXGBE_DESCS_PER_LOOP, just return no packet
 *   numbers of DD bit
 * - floor align nb_pkts to a RTE_IXGBE_DESC_PER_LOOP power-of-two

> Med venlig hilsen / kind regards
> - Morten Brørup

  reply	other threads:[~2020-07-16  8:50 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-15 16:02 Morten Brørup
2020-07-16  8:49 ` Zhao1, Wei [this message]
2020-07-16  9:08   ` [dpdk-dev] ixgbe vector rx does not conform torte_eth_rx_burst() API Morten Brørup
2020-07-17 13:49     ` Bruce Richardson
2020-07-18  3:32     ` Zhao1, Wei
2020-07-18  3:44       ` Zhao1, Wei
2020-07-27  9:42         ` [dpdk-dev] ixgbe vector rx does not conform to rte_eth_rx_burst() API Morten Brørup
2020-07-27 10:35           ` Zhao1, Wei

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