performance measurement & rate monotonic related queries

Salman unix at
Mon Mar 17 14:24:23 UTC 2003

Hi guys,

As you know, in an SCI based compute cluster, a memory segment of each
node gets shared, where all nodes can access the shared memory, hence
use it in aid of cluster computing.

A simple view of it, is to think a section of physical memory address is
mapped to a remote node, where the remote node can read and write to it,
just like part of its local memory address.

My questions are:

1. is there any way, which I can find out for a simple operation (eg a
simple write RemoteMappedAddress = 0;) how many context swicthes,
interrupts, instructions take place? (it should be only one operation,
but I believe dependant on configuration of SCI card it can be variable,
and i'd like to measure it)

2. what's the best way of measuring the latency of such simple operation
? can I use rate monotonic, and decrease period until it time-outs ?

3. when you specify a rate monotonic period (lets say 10 milliseconds),
are these 10 milliseconds purely execution of my task, or do they
include clock ticks and other rate monotonic operations as well?

4. How can I ensure that no interrupt, context switch, task switch, etc
take place while a specific task is running ? can I achieve this but
assigning it a high priority ? or placing it within rate monotonic



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