opensm: file routing engine

I've been toying with the file routing engine implementation for some work I'm doing, but I'm finding very little documentation on it. I only have one switch to experiment with at the moment as well so some of the information in the lid / lfts files that are generated are not obvious for how they expand to a multiple switch environment. Perhaps there is a document around since I'm a RTFM type of person?

At any rate, here's what I've gathered with 4. being the big question.

1. The easiest way to get started with the file routing engine is to generate the lid / lfts using a different routing engine. I went ahead and did the following: opensm -D 0x40 -R ftree
2. Once run, copy the /var/log/opensm-lfts.dump and /var/log/opensm-lid-matrix.dump files elsewhere for use
3. I've tried to generalize the file contents below
4. Modify the opensm-lid-matrix.dump file to "implement" or "tweak" the routing algorithm over the physical network?
5. Run opensm -R file -M new-lid-matrix.dump -U new-lfts.dump

I have one other strange question ... is it possible to carve a single physical switch into two logical switches (put a cable between ports 16/17 and modify the routing tables ... this seems like it wouldn't work as the Unicast LID / Switch: guid rows in the respective files below serve as keys so the single switch would be identified twice).

The file formats seem to be:

opensm-lfts.dump (later becomes -U [file])
- Contains all discovered ports (powered on), their function (Switch vs. Channel Adapter), their LID and some extra information. This is essentially the physical network (if all machines are powered on) ... the format is:
Unicast lids [0-x] of switch Lid LID# guid <GUID> ('switch description'):
<LID 0xZZZZ> <SwitchPort ZZZ> # <Channel Adapter | Switch> portguid <GUID>: 'Descirption'

I assume this file grows with all of the Channel Adapters and switches. Given a switch-switch connection a row would look like
0x0019 005 # Switch portguid 0x000000000000003 'MF3:switch-my:MTS3600/U1'

You could essentially use this file to map the entire physical network, you would end up with a graph ... but no information for how to traverse it efficiently, does that sound right?

opensm-lid-matrix.dump
- Looks like it contains the hop information ... but it's a bit more cryptic since I have only one switch :( It should contain a list of all switches, the LID for the switch and then hop information. The hop information is what I'm a bit puzzled about here, as well as what port guid information is tacked on. The format of the file is:
Switch: guid 0x000000000000x
<LID 0xZZZZ> 00 ff ff <hops for all ports> # portguid 0x0000000

I know ... it's a detailed question but I figured I would write enough so someone else wouldn't have to reverse engineer using the file routing engine if this is basically right.

Paul Monday
Parallel Scientific, LLC

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Quoted 5 lines

I have one other strange question ... is it possible to carve a single physical switch into two logical switches (put a cable between ports 16/17 and modify the routing tables ... this seems like it wouldn't work as the Unicast LID / Switch: guid rows in the respective files below serve as keys so the single switch would be identified twice).

Not that I am aware of. When you say you have a single switch I assume you mean a switch based on a single switch ASIC? Like a 24 or 36 port "pizza box" switch.

The file formats seem to be:

opensm-lfts.dump (later becomes -U [file])
- Contains all discovered ports (powered on), their function (Switch vs. Channel Adapter), their LID and some extra information. This is essentially the physical network (if all machines are powered on) ... the format is:
Unicast lids [0-x] of switch Lid LID# guid<GUID> ('switch description'):
<LID 0xZZZZ> <SwitchPort ZZZ> #<Channel Adapter | Switch> portguid <GUID>: 'Descirption'

I assume this file grows with all of the Channel Adapters and switches.
Given a switch-switch connection a row would look like
0x0019 005 # Switch portguid 0x000000000000003 'MF3:switch-my:MTS3600/U1'
Yes this file grows with more nodes in the system. But the line above is not a connection but rather a linear forwarding table entry. In general, this is saying that for the given lid "0x0019" route out port 5 of that switch (the switch given by the "Unicast lids [..." line. The information after '#' is more information about the node with lid=0x0019. This is _not_ the other end of the link on port 5.

The topology of the physical connections are shown in opensm-subnet.lst.

Quoted 3 lines

You could essentially use this file to map the entire physical network, you would end up with a graph ... but no information for how to traverse it efficiently, does that sound right?

No this is not mapping the physical network. It is a dump of the port forwarding which was programed into each switch by opensm.

Changing this file is what allows you to change the routing and then feed it back into opensm.

Quoted 8 lines

opensm-lid-matrix.dump
- Looks like it contains the hop information ... but it's a bit more cryptic since I have only one switch :( It should contain a list of all switches, the LID for the switch and then hop information. The hop information is what I'm a bit puzzled about here, as well as what port guid information is tacked on. The format of the file is:
Switch: guid 0x000000000000x
<LID 0xZZZZ> 00 ff ff<hops for all ports> # portguid 0x0000000

That is the switch to switch hop count information. Probably not of much use with only 1 switch.

Thank you, your detail is greatly appreciated :)

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Quoted 5 lines

I have one other strange question ... is it possible to carve a single physical switch into two logical switches (put a cable between ports 16/17 and modify the routing tables ... this seems like it wouldn't work as the Unicast LID / Switch: guid rows in the respective files below serve as keys so the single switch would be identified twice).

Not that I am aware of. When you say you have a single switch I assume you mean a switch based on a single switch ASIC? Like a 24 or 36 port "pizza box" switch.

Yes, a 36 port Mellanox pizza box with a single crossbar ... based on how I read these files, it looks like they key off a single GUID that identifies the switch ... which would probably make the subnet manager unhappy if I arbitrarily tried to mock it up being two switches somehow

Quoted 11 lines

The file formats seem to be:

opensm-lfts.dump (later becomes -U [file])
- Contains all discovered ports (powered on), their function (Switch vs. Channel Adapter), their LID and some extra information. This is essentially the physical network (if all machines are powered on) ... the format is:
Unicast lids [0-x] of switch Lid LID# guid<GUID> ('switch description'):
<LID 0xZZZZ> <SwitchPort ZZZ> #<Channel Adapter | Switch> portguid <GUID>: 'Descirption'

Quoted 4 lines

I assume this file grows with all of the Channel Adapters and switches.
Given a switch-switch connection a row would look like
0x0019 005 # Switch portguid 0x000000000000003 'MF3:switch-my:MTS3600/U1'
Yes this file grows with more nodes in the system. But the line above is not a connection but rather a linear forwarding table entry. In general, this is saying that for the given lid "0x0019" route out port 5 of that switch (the switch given by the "Unicast lids [..." line. The information after '#' is more information about the node with lid=0x0019. This is _not_ the other end of the link on port 5.

Ahhh, I see ... so this table could get quite large ... if I have 1,000 nodes in a subnet, each with a LID assigned, this table would become quite large as each LID would be listed for each switch if I have my forwarding thoughts in my head ... maybe I need to wander around and steal another switch from someone ;-)

Quoted 1 line

The topology of the physical connections are shown in opensm-subnet.lst.

Ahhh, but the opensm-subnet.lst is not handed to the file routing algorithm ... this must be "derived" at runtime each run I'm guessing and then dumped to /var/log. Very helpful! Thank you for the pointer.

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Quoted 3 lines

You could essentially use this file to map the entire physical network, you would end up with a graph ... but no information for how to traverse it efficiently, does that sound right?

No this is not mapping the physical network. It is a dump of the port forwarding which was programed into each switch by opensm.

Changing this file is what allows you to change the routing and then feed it back into opensm.

Quoted 8 lines

opensm-lid-matrix.dump
- Looks like it contains the hop information ... but it's a bit more cryptic since I have only one switch :( It should contain a list of all switches, the LID for the switch and then hop information. The hop information is what I'm a bit puzzled about here, as well as what port guid information is tacked on. The format of the file is:
Switch: guid 0x000000000000x
<LID 0xZZZZ> 00 ff ff<hops for all ports> # portguid 0x0000000

Quoted 1 line

That is the switch to switch hop count information. Probably not of much use with only 1 switch.

Ugh ... I need another switch or .dump files from someone ... I haven't found any stray .dump files out on the network, but then, Google knows all and someone must have posted a couple somewhere to play with.

Thank you so much again Ira, I wasn't too far off and mostly it seems I'm off in places that having only a single switch wouldn't let me see. The semantic correction of opensm-lfts.dump was critical.

Cheers, have a wonderful weekend.

Paul Monday
Parallel Scientific, LLC