Re: rdma_connect() "timeout"

[Yann Droneaud <ydroneaud-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org>]

Hi,

Le mercredi 18 juillet 2012 à 15:49 +0000, Hefty, Sean a écrit :
> > Is there a way to setup the timeout in rdma_connect() ?
> 
> For IB, the timeout is based on the packet lifetime in the path record returned by the SA.  
> The rdma_cm will retry a CM REQ the maximum number of times (15).
>  

According to the OpenSM default configuration (/usr/sbin/opensm
--create-config <config>) :

  # The subnet_timeout code that will be set for all the ports
  # The actual timeout is 4.096usec * 2^<subnet_timeout>
  subnet_timeout 18

  # The code of maximal time a packet can live in a switch
  # The actual time is 4.096usec * 2^<packet_life_time>
  # The value 0x14 disables this mechanism
  packet_life_time 0x12

Despite the notation, they are the same values.

It gives me:

 4.096 * 10^-6 * 2^18 = 1.074 s

 15 * subnet timeout / packet life time = 16.106 s ... 

This is a lot less than 98 s.

Where does come the difference ?

> > Is there a way to change the CM parameters ? e.g. "Service Timeout" to
> > wait for moving from "REP wait" state to "Timeout" state, and the number
> > of send "REQ" retries (From 12.9.5 "Communication Establishement and
> > Release - Active") ?
> 
> There is no direct way to change the timeout parameter.  You would need to adjust the subnet timeout values at the SA.

Is it subnet_timeout or packet_life_time ?

Thanks for your answers.

Regards.

-- 
Yann Droneaud
OPTEYA


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