[ovs-dev] Datpath in openVswitch

Vivek Kumar (EPG) kvivek at juniper.net
Thu Nov 21 05:29:34 UTC 2013


Hi Ben,
Thanks a lot for response.


data flow means Ethernet net packet traversing, so my doubt is:
  
1) After the packet receiving from Ethernet driver packet will traverse in  kernel space or in user space.
2) This rule is applicable for all packet or first packet


Thanks,
Vivek


-----Original Message-----
From: Ben Pfaff [mailto:blp at nicira.com] 
Sent: Wednesday, November 20, 2013 10:41 PM
To: Vivek Kumar (EPG)
Cc: discuss at openvswitch.org; dev at openvswitch.org
Subject: Re: Datpath in openVswitch

On Wed, Nov 20, 2013 at 10:40:31AM +0000, Vivek Kumar (EPG) wrote:
> 1) could you please confirm in OpenVswitch data flow to be @ kernel level or user level.

What's a data flow?

> 2) As some document says that When the first packet of a flow comes to 
> the datapath, the datapath transmit it to the userspace using netlink. 
> Does the datapath buffer the packet? Or it is just buffered in 
> userspace?

The datapath does not buffer.

> 3) Will this (first)packet traversing from kernel to user space and 
> user space to kernel space affect the performance.

Yes.

> 4) It seems that datapath flow entry is 5 seconds time-out, then how 
> soon is the facet time_out? Where can I find the code of time_out? Or 
> can we change time out value.

The maximum timeout is 5 seconds.  ofproto-dpif.c.  Modify the code.






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