[ofa-general] [PATCH] opensm/doc/current-routing.txt: added ucast cache info

[Yevgeny Kliteynik]

Added ucast cache info in current-routing.txt

Signed-off-by: Yevgeny Kliteynik <kliteyn at dev.mellanox.co.il>
---
 opensm/doc/current-routing.txt |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/opensm/doc/current-routing.txt b/opensm/doc/current-routing.txt
index 2bb6c2f..af008bc 100644
--- a/opensm/doc/current-routing.txt
+++ b/opensm/doc/current-routing.txt
@@ -28,6 +28,17 @@ two switches.  This provides deadlock free routes for hypercubes when
 the fabric is cabled as a hypercube and for meshes when cabled as a
 mesh (see details below).

+OpenSM provides an optional unicast routing cache (enabled by -A or
+--ucast_cache options). When enabled, unicast routing cache prevents
+routing recalculation (which is a heavy task in a large cluster) when
+there was no topology change detected during the heavy sweep, or when
+the topology change does not require new routing calculation, e.g. when
+one or more CAs/RTRs/leaf switches going down, or one or more of these
+nodes coming back after being down.
+A very common case that is handled by the unicast routing cache is host
+reboot, which otherwise would cause two full routing recalculations: one
+when the host goes down, and the other when the host comes back online.
+
 OpenSM also supports a file method which can load routes from a table. See
 modular-routing.txt for more information on this.

-- 
1.5.1.4