README,v 1.2 2003/07/14 15:32:01 pradeep Exp

Description:

This test check for priority inversion when using different RTCORBA
configurations.  The following four configurations are tested:

(a) Thread lanes without bands
(b) Thread lanes with bands
(c) Thread pool without bands
(d) Thread pool with bands

The server has a servant registered with a POA serviced by a thread
pool without lanes and another servant registered with a POA serviced
by a thread pool with lanes.  The thread pool with lanes has a low and
a high priority lane.

The client makes several oneway low priority invocations followed by
several oneway high priority invocations.  Each invocation performs
about 2 seconds of CPU bound work.  Priority inversion occurs if low
priority invocations get processed before high priority invocations.

(a) shows the best result of high priority requests getting serviced
before low priority requests even though low priority requests were
sent before high priority requests.  This is because low priority
invocations are processed by the low priority lane and high priority
invocations are processed by the high priority lane.  In addition, low
priority requests are sent on a different connection than the high
priority requests since each lane has a different endpoint.

(b) does not improve on (a) since the requests are already sent on
different connections.

(c) shows priority inversion as low priority requests get processed
before high priority requests.  This is because only one connection is
used for both low and high priority requests.  Therefore, the high
priority requests are queued behind the low priority requests. 

(d) shows improvement on (c) since using bands allows the high
priority requests to go on a different connection than the low
priority requests.  However, priority inversion still exists since the
server does not distinguish between the low priority connection and
the high priority connection and therefore treats them equally.
Removing this priority inversion will require two improvements: (1)
band information needs to be propagated to the server when a banded
connection is established by the client; (2) server side dispatching
needs to be based on the priority of the connections.

See run_test.pl to see how to run this test.  The server
static_threads should be set to the number of CPUs on the machine.