p2p routing

[Peter_Heseltine]

I have 7 flexrio cards 5 7965 and 2 7961 and am heavily using P2P streaming to transfer data between them. The chassis is a PXIe-1065. Having enable all the P2P connections is there anyway of knowing which of the links go by the backplane switches and which have to use the host PC?

[BenClark]

Hi Peter,

Sorry for the delay in getting back to you, I have been trying to find out if there is a way of doing this but so far I have had no luck. Currently, checking the backplane connections themselves should give a good indication on how they are connected, for example if they are spaced between a backplane separator then they are probably using the host.

Is there a specific reason for needing to know this information, for example needing the full 800 MB/s+ speeds that a direct route provides?

[Peter_Heseltine]

Ben,

Thanks for the reply. This is an issue for me as some of the data I am transferring seems to be dependent on host load and i therefore suspect some of my P2P connections may be using the host. The P2P Vi's allow you to make connections between writers and readers but they give no indication of which route it has used so i cannot confirm my suspicions. Some of the connections are low datarate and some are very high so i would like to be able to arrange for the high datarates to use the backplane switches. Maybe a suggestion for future updates of Labview ?

Peter

[BenClark]

The P2P connections should all take a direct (or the most direct) route to each other:

From looking at this diagram, I can say that P2P connections on boards 9-14 should route through the chassis' PCIe Switch and should therefore communicate at expected P2P speeds.

A P2P connection to a card in slot 7 or 8 will be entirely dependent on the architecture of the controller. In addition to this, if multiple streams are transferred through the same switch then the 800 MB/s maximum transfer speed will be distributed (Two simultaneous transfers using four cards should mean that you experience a transfer rate slightly below 400 MB/s). Does this fit with the pattern of data rates you are experiencing?

[Peter_Heseltine]

Ben,

The cards I am using are fitted into slots 8 -14. The host load depndant symptoms I am seeing are not related to the P2P transfer between 8 and 9. For slots 9-14 is it guaranteed that a P2P connection will not use the host? Also is there any info on what role the host PC plays in setting up and monitoring all P2P connections because once established  they are not entirely separate from interaction with the host?

Thanks for your help so far.

Peter

[BenClark]

Hi Peter,

Apologies for the delay, but I'll need to talk to some FlexRIO/PXI specialists about this, I will let you know as soon I can find out more information.

[BenClark]

Hi Peter,

As far as I have been able to find out the P2P connection for slots 9-14 should not use the host, but I have posed the question to the US team as they should be able to give a definitive answer.

The host is able to monitor the connections regarding the data in the streams using niP2P Property Nodes and Events.
 but there seems to no similar method of obtaining information about the stream.

I hope to have more information for you soon.

[Peter_Heseltine]

Ok thanks i await the reply with interest.

Thanks for your help

Peter