[ofa-general] Toward next OFED release (1.3)

Hal Rosenstock halr at voltaire.com
Wed Jul 11 08:54:06 PDT 2007 

On Tue, 2007-07-10 at 15:12, Hal Rosenstock wrote:
> On Tue, 2007-07-10 at 15:11, Peter Kjellstrom wrote:
> > On Tuesday 10 July 2007, Hal Rosenstock wrote:
> > ...
> > > > Management:
> > > >       * Multiple partitions
> > > >       * OpenSM
> > > >               * More routing performance improvements
> > > >               * Even more speedups
> > > >               * Better packaging/installation
> > > >               * “Native” daemon mode
> > > >               * Performance management
> > > >               * Quality of Service manager: Based on IBTA annex
> > >
> > > enhancements for fat tree routing (non pure tree support)
> > > more console commands and telnet access to console
> > 
> > Pardon my ignorance, but could you elaborate on what a "non-pure tree" is and 
> > in which way OFED-1.2 opensm performs badly for these?

The following patch contains some of the answers to the above:

-----Forwarded Message-----

From: Yevgeny Kliteynik <kliteyn at dev.mellanox.co.il>
To: Hal Rosenstock <halr at voltaire.com>
Cc: OpenIB <general at lists.openfabrics.org>
Subject: [PATCH 2/2] osm: updating doc with root and compute nodes options for fat-tree
Date: 09 Jul 2007 11:32:49 +0300

Hi Hal.

Updating doc and osm manpage with the 
recent enhancement of fat-tree routing.

Signed-off-by: Yevgeny Kliteynik <kliteyn at dev.mellanox.co.il>
---
 opensm/doc/current-routing.txt |   28 ++++++++++++++++++++++------
 opensm/man/opensm.8            |   33 ++++++++++++++++++++++++++-------
 2 files changed, 48 insertions(+), 13 deletions(-)

diff --git a/opensm/doc/current-routing.txt b/opensm/doc/current-routing.txt
index 9852ef0..76f91ba 100644
--- a/opensm/doc/current-routing.txt
+++ b/opensm/doc/current-routing.txt
@@ -174,11 +174,14 @@ Fat-tree Routing Algorithm
 Purpose:
 
 The fat-tree algorithm optimizes routing for "shift" communication pattern.
-It should be chosen if a subnet is a symmetrical fat-tree of various types.
+It should be chosen if a subnet is a symmetrical or almost symmetrical
+fat-tree of various types.
 It supports not just K-ary-N-Trees, by handling for non-constant K,
 cases where not all leafs (CAs) are present, any CBB ratio.
 As in UPDN, fat-tree also prevents credit-loop-deadlocks.
-Fat-tree algorithm supports topologies that comply with the following rules:
+
+If the root guid file is not provided ('-a' or '--root_guid_file' options),
+the topology has to be pure fat-tree that complies with the following rules:
   - Tree rank should be between two and eight (inclusively)
   - Switches of the same rank should have the same number
     of UP-going port groups*, unless they are root switches,
@@ -189,18 +192,31 @@ Fat-tree algorithm supports topologies that comply with the following rules:
     of ports in each UP-going port group.
   - Switches of the same rank should have the same number
     of ports in each DOWN-going port group.
-*ports that are connected to the same remote switch are referenced as
+  - All the CAs have to be at the same tree level (rank).
+
+If the root guid file is provided, the topology doesn't have to be pure
+fat-tree, and it should only comply with the following rules:
+  - Tree rank should be between two and eight (inclusively)
+  - All the Compute Nodes** have to be at the same tree level (rank).
+    Note that non-compute node CAs are allowed here to be at different
+    tree ranks.
+
+* ports that are connected to the same remote switch are referenced as
 'port group'.
+** list of compute nodes (CNs) can be specified by '-u' or '--cn_guid_file'
+OpenSM options.
 
 Note that although fat-tree algorithm supports trees with non-integer CBB
 ratio, the routing will not be as balanced as in case of integer CBB ratio.
 In addition to this, although the algorithm allows leaf switches to have any
 number of CAs, the closer the tree is to be fully populated, the more effective
 the "shift" communication pattern will be.
+In general, even if the root list is provided, the closer the topology to a
+pure and symmetrical fat-tree, the more optimal the routing will be.
 
-The algorithm also dumps CA ordering file (opensm-ftree-ca-order.dump) in the
-same directory where the OpenSM log resides. This ordering file provides the
-CA order that may be used to create efficient communication pattern, that
+The algorithm also dumps compute node ordering file (opensm-ftree-ca-order.dump)
+in the same directory where the OpenSM log resides. This ordering file provides
+the CN order that may be used to create efficient communication pattern, that
 will match the routing tables.
 

diff --git a/opensm/man/opensm.8 b/opensm/man/opensm.8
index 5f34cd1..5472faf 100644
--- a/opensm/man/opensm.8
+++ b/opensm/man/opensm.8
@@ -603,7 +603,7 @@ UPDN Algorithm Usage
 Activation through OpenSM
 
 Use '-R updn' option (instead of old '-u') to activate the UPDN algorithm.
-Use '-a <guid_list_file>' for adding an UPDN guid file that contains the
+Use '-a <root_guid_file>' for adding an UPDN guid file that contains the
 root nodes for ranking.
 If the `-a' option is not used, OpenSM uses its auto-detect root nodes
 algorithm.
@@ -621,12 +621,14 @@ it exists) that connects the CA to the subnet as a root node.
 Fat-tree Routing Algorithm
 
 The fat-tree algorithm optimizes routing for "shift" communication pattern.
-It should be chosen if a subnet is a symmetrical fat-tree of various types.
+It should be chosen if a subnet is a symmetrical or almost symmetrical
+fat-tree of various types.
 It supports not just K-ary-N-Trees, by handling for non-constant K,
 cases where not all leafs (CAs) are present, any CBB ratio.
 As in UPDN, fat-tree also prevents credit-loop-deadlocks.
 
-The Fat-tree algorithm supports topologies that comply with the following rules:
+If the root guid file is not provided ('-a' or '--root_guid_file' options),
+the topology has to be pure fat-tree that complies with the following rules:
   - Tree rank should be between two and eight (inclusively)
   - Switches of the same rank should have the same number
     of UP-going port groups*, unless they are root switches,
@@ -637,10 +639,21 @@ The Fat-tree algorithm supports topologies that comply with the following rules:
     of ports in each UP-going port group.
   - Switches of the same rank should have the same number
     of ports in each DOWN-going port group.
+  - All the CAs have to be at the same tree level (rank).
 
-Note: ports that are connected to the same remote switch are referenced as
+If the root guid file is provided, the topology doesn't have to be pure
+fat-tree, and it should only comply with the following rules:
+  - Tree rank should be between two and eight (inclusively)
+  - All the Compute Nodes** have to be at the same tree level (rank).
+    Note that non-compute node CAs are allowed here to be at different
+    tree ranks.
+
+* ports that are connected to the same remote switch are referenced as
 \'port group\'.
 
+** list of compute nodes (CNs) can be specified by \'-u\' or \'--cn_guid_file\'
+OpenSM options.
+
 Topologies that do not comply cause a fallback to min hop routing.
 Note that this can also occur on link failures which cause the topology
 to no longer be "pure" fat-tree.
@@ -650,15 +663,21 @@ ratio, the routing will not be as balanced as in case of integer CBB ratio.
 In addition to this, although the algorithm allows leaf switches to have any
 number of CAs, the closer the tree is to be fully populated, the more
 effective the "shift" communication pattern will be.
+In general, even if the root list is provided, the closer the topology to a
+pure and symmetrical fat-tree, the more optimal the routing will be.
 
-The algorithm also dumps CA ordering file (opensm-ftree-ca-order.dump) in the
-same directory where the OpenSM log resides. This ordering file provides the
-CA order that may be used to create efficient communication pattern, that
+The algorithm also dumps compute node ordering file (opensm-ftree-ca-order.dump)
+in the same directory where the OpenSM log resides. This ordering file provides
+the CN order that may be used to create efficient communication pattern, that
 will match the routing tables.
 
 Activation through OpenSM
 
 Use '-R ftree' option to activate the fat-tree algorithm.
+Use '-a <root_guid_file>' to provide root nodes for ranking. If the `-a' option
+is not used, routing algorithm will detect roots automatically.
+Use '-u <root_cn_file>' to provide the list of compute nodes. If the `-u' option
+is not used, all the CAs are considered as compute nodes.
 
 Note: LMC > 0 is not supported by fat-tree routing. If this is
 specified, the default routing algorithm is invoked instead.
-- 
1.5.1.4

> Yevgeny,
> 
> Could you elaborate on this ? Thanks.
> 
> -- Hal
> 
> > Or maybe there are some nice docs for me to sink my teeth into...
> > 
> > /Peter
> > 
> > ______________________________________________________________________
> > 
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