Tuesday Tiny Techie Tip


uptime is a little gadget that tells you some of the vital information about the host you're logged in to. (bonus tip: never use a preposition to end your sentences with.)
hugo% uptime
 12:01pm  up 32 days, 16:21,  14 users,  load average: 0.36, 0.52, 0.47

It tells me that it's a minute past noon, that hugo (my current host) has been up for 32 days 16 hours and 21 minutes, that there are currently 14 login sessions running, and three numbers indicating how busy the system is.

The "load average" numbers indicate the average number of jobs in the run queue over the last 1, 5, and 15 minutes. It's arguable how useful these numbers are, but you can make some generalizations. If the load is very close to 0, then probably no one is doing anything in particular at the moment. If it's 1 or more, then the system is pretty busy since at least one job was always waiting for the cpu.

It's useful to note that these numbers are the same ones used by Clearcase when it's looking for distributed build hosts. Each of our build hosts can be configured to deny build requests if its idle percentage is below a certain level. The Clearcase bldserver.control(4) man page gives an interesting little chart giving a correspondence between reported load and idle percentage:

Load    Idle Percentage
0.0     100
0.5     68
1.0     47
2.0     22
4.0     almost 0

Of course, this is all assuming single processor systems so if we had any multi-processor boxes around, things would get a little more complicated.

Tuesday Tiny Techie Tip -- 6 May 1997
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Written by Jeff Youngstrom

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Tuesday Tiny Techie Tips are all © Copyright 1996-1997 by Jeff Youngstrom. Please ask permission before reproducing any of this material.