Setting ACK timeout for QP's created using RDMA_CM.

Setting ACK timeout for QP's created using RDMA_CM.

[Hari Subramoni]

Hi,

I am looking for the IB equivalent of the 're-transmission timeout' we
have in ethernet. I was going through the QP attributes and came across
this field in 'struct ibv_qp_attr'

uint8_t timeout; /* Local ack timeout for primary path (valid only for RC QPs)*/

I believe that this is the period of time (in seconds) that the IB HCA
will wait for the ACK for a packet it sent out before re-transmitting? I
was looking as to whether this field can be modified when creating a QP
using RDMA_CM.

Thanks in advance,

Hari.


--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

RE: Setting ACK timeout for QP's created using RDMA_CM.

[Hefty, Sean]

>uint8_t timeout; /* Local ack timeout for primary path (valid only for RC
>QPs)*/
>
>I believe that this is the period of time (in seconds) that the IB HCA
>will wait for the ACK for a packet it sent out before re-transmitting? I
>was looking as to whether this field can be modified when creating a QP
>using RDMA_CM.

This field is set based on the packet lifetime carried in the path record.  If you're using opensm, there's probably a configuration option that can adjust this (subnet timeout, maybe?).  The time given for the QP attribute is in 'IB time': 4.096 x 2 ^ timeout micro-seconds.

- Sean
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

RE: Setting ACK timeout for QP's created using RDMA_CM.

[Hari Subramoni]

Hi Sean,

Thanks a lot for the quick and detailed response... :).

Hari.

On Fri, 29 Jan 2010, Hefty, Sean wrote:

> >uint8_t timeout; /* Local ack timeout for primary path (valid only for RC
> >QPs)*/
> >
> >I believe that this is the period of time (in seconds) that the IB HCA
> >will wait for the ACK for a packet it sent out before re-transmitting? I
> >was looking as to whether this field can be modified when creating a QP
> >using RDMA_CM.
>
> This field is set based on the packet lifetime carried in the path record.  If you're using opensm, there's probably a configuration option that can adjust this (subnet timeout, maybe?).  The time given for the QP attribute is in 'IB time': 4.096 x 2 ^ timeout micro-seconds.
>
> - Sean
>

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Setting ACK timeout for QP's created using RDMA_CM.

[Hal Rosenstock]

On Fri, Jan 29, 2010 at 11:43 AM, Hefty, Sean <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:
>>uint8_t timeout; /* Local ack timeout for primary path (valid only for RC
>>QPs)*/
>>
>>I believe that this is the period of time (in seconds) that the IB HCA
>>will wait for the ACK for a packet it sent out before re-transmitting? I
>>was looking as to whether this field can be modified when creating a QP
>>using RDMA_CM.
>
> This field is set based on the packet lifetime carried in the path record.  If you're using opensm, there's probably a configuration option that can adjust this (subnet timeout, maybe?).

Yes, OpenSM returns subnet_timeout as the SA PathRecord PacketLifeTime
assuming it's not loopback and no QoS set.

-- Hal

>  The time given for the QP attribute is in 'IB time': 4.096 x 2 ^ timeout micro-seconds.
>
> - Sean
> --
> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html