[ofa-general] opensm support for toroidal meshes

[Sasha Khapyorsky]

Hi Bob,

On 15:47 Mon 10 Nov     , Robert Pearson wrote:
> We have been involved in a project to deliver a large system based on a
> toroidal mesh fabric. One of the requirements for this system is to be able
> to guarantee a deadlock free routing of the fabric. The lash routing engine
> in opensm did not work in this case because required number of VLs for the
> machine as configured was 12 which exceeded the number of VLs supported by
> Mellanox switch ASICs. It turns out that if one has the freedom to reorder
> the order of the port assignments used by lash optimally that lash can
> successfully route the fabric but that is impractical in the hardware. The
> attached note describes an algorithm for automatically recognizing when a
> Cartesian mesh fabric is a torus, determining its size and optimally
> reordering the ports in opensm so that lash can generate a route with the
> smallest number of VLs.
> 
> We have implemented a set of changes to opensm that implement this algorithm
> and will submit the changes as patches. This note will help to understand
> the code.

Thanks for the great work! I'm sending some initial comments (still
learning the code).

Sasha

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