Re: [dpdk-dev] Fast Path Query

["Zhang, Helin" <helin.zhang@intel.com>]

Hi Deepak

Exception path or KNI just provide an exceptional path for packet exchanging between user space and kernel space. All packet IO are still in user space DPDK, Linux kernel still doesn’t know the NIC port. So, no standard Linux interrupt.

Regards,
Helin

From: Deepak Sehrawat [mailto:d.sehrawat@gmail.com]
Sent: Wednesday, January 14, 2015 3:58 PM
To: Zhang, Helin
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] Fast Path Query


Hi Helin,

If we use exception_path or KNI, which extracts packet from Linux kernel (for DPDK application processing), will it still remain fast path? Will it not impact the performance; as Linux interrupt framework shall also come into picture here?


On Wed, Jan 14, 2015 at 1:17 PM, Zhang, Helin <helin.zhang@intel.com<mailto:helin.zhang@intel.com>> wrote:
Hi Deepak

If a NIC port is controlled by DPDK, all packets received by that port will go directly to DPDK, and Linux kernel doesn't know those packets anymore.
But, the packets received by DPDK can be put into kernel by two special ways. They are exception_path and KNI. Please check the examples/ for more details.
In the future, a port may be co-controlled by both Linux and DPDK. Part of queues will be controlled by Linux kernel driver, part of queues will be controlled by DPDK. Check the DPDK roadmap for more details.

Regards,
Helin

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org<mailto:dev-bounces@dpdk.org>] On Behalf Of Deepak Sehrawat
> Sent: Wednesday, January 14, 2015 2:16 PM
> To: dev@dpdk.org<mailto:dev@dpdk.org>
> Subject: [dpdk-dev] Fast Path Query
>
> Hi All,
>
> I have a use-case where my slow path application (control path) is to run on
> Linux where as my data path is to run as DPDK application. Because both
> control and data packets are going to be received via same NIC card, how will
> these two flows be separated and passed on to Linux control app and DPDK
> data path app respectively? In short I want to understand how NIC received
> packets are separated between Linux Eth driver and PMD (poll mode
> driver) of DPDK?
>
> Thanks for the help in advance.
>
> Thanks,
> Deepak



--
======================================
                     The Harder I work,
                     The Luckier I Get
----------------------------------------------------------------------------

DEEPAK $EHRAWAT
Senior Principal Engineer
Hughes Systique Corporation,
D-8, InfoCity Phase- II,
Sector-33, Gurgaon-122001
Mobile No. 9818228349
deepak.sehrawat@hsc.com<mailto:deepak.sehrawat@hsc.com>
======================================