[openib-general] LID assignment policy of opensm

[Hal Rosenstock]

Hi Devesh,

On Thu, 2006-03-02 at 23:31, Devesh Sharma wrote:
> On 02 Mar 2006 08:35:04 -0500, Hal Rosenstock <halr at voltaire.com>
> wrote:
>         Hi Devesh,
>         
>         On Thu, 2006-03-02 at 08:03, Devesh Sharma wrote:
>         > Hi All,
>         > I have another query regarding Opensm,
>         > What is MLID assignment policy?
>         > Is there any porvision that MLID assigned by Opensm may
>         always remain 
>         > in 0xC001 0xC0FF range, In case by underliying hardware only
>         255
>         > seprate multicast groups are supported at a time?
>         
>         OpenSM does not overlay multiple groups (MGIDs) with the same
>         characteristics on the same MLID. It uses unique MLIDs per
>         group.
> 
> This is fine, each group will have unique MLID though  they have same
> characteristics, I am trying to know is,
> as in unicast LID assignment there is a file maintained by SM, so for
> MLID is there any such mapping file 

No.

> or this is maintained in some internal structure,

The MLIDs in use are maintained in an internal structure.

>  or every create request with new MGID will be given One higher MLID
> from MLID assigned to previous create request and as the
> switchInfo::MulticastFDBCap is reached, create request will fail?

Sort of. MLIDs are also returned when the group is reclaimed some time
after it is deleted (last full member leaves). That leaves holes in the
table so it is not a simple increment. Requests fail when a new group
creation would cause there to be MLIDs in use greater than the lowest
SwitchInfo:MulticastFDBCap in the subnet.

I'm not sure what your concern is here.

-- Hal

>         MLIDs start at 0xC000 and are constrained by the least capable
>         switch
>         (in terms of SwitchInfo::MulticastFDBCap). 
>         
>         Are you just asking or are you having some issue in this area
>         ?
> 
> I am just asking about this. 
> 
>         -- Hal
>         
>         
>