Re: tune ib stack

[Sebastian Riemer <sebastian.riemer-EIkl63zCoXaH+58JC4qpiA@public.gmane.org>]

On 09.04.2013 15:34, Hal Rosenstock wrote:
> On 4/9/2013 9:16 AM, Sebastian Riemer wrote:
>> On 09.04.2013 14:49, Hal Rosenstock wrote:
>>> On 4/9/2013 7:12 AM, Vasiliy Tolstov wrote:
>>>> Hello. I have some servers, with mellanox ConnectX-3 and have some questions:
>>>> Why max_mtu differs with active_mtu? 
>>>
>>> What does peer port say for max MTU ?
>>>
>>>> How can i set active mtu?
>>>
>>> SM sets active MTU to min of peer ports max MTUs.
>>
>> So with "peer port max MTU" do you mean this file?:
>>
>> /sys/class/infiniband/mlx4_0/device/mlx4_port1_mtu
> 
> I meant NeighborMTU from PortInfo as active MTU and MTUCap there is
> supported MTU.

So these values are exactly the same as in "ibv_devinfo" and can be set
in /sys/class/infiniband/mlx4_0/device/mlx4_port1_mtu.

I've found the PortInfo with the command
"smpquery portinfo -C mlx4_0 3 1"
where I'm using the first HCA to contact the SM. I tell the SM the
destination LID ('3' here in my case) and the destination port ('1').

Is there another method to set the max MTU?

I know that switches can also set the max MTU for their switch ports
where most of them use 2048 as default.
How to change these switch port MTUs for unmanaged switches?

On managed switches this can be done over the web front-end.

Cheers,
Sebastian
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