Mach Factor zero while system is almost idle

[Geert Van Pamel]

I have a strange problem on an AlphaServer DS20A running Tru64 V5.1.

Ths system is almost idle today.

vmstat 5
Virtual Memory Statistics: (pagesize = 8192)
procs memory pages intr cpu
r w u act free wire fault cow zero react pin pout in sy cs us sy id
4 245 43 107K 3927 14K 74M 15M 23M 156 16M 298 10 3K 335 0 1 99
3 246 43 107K 3932 14K 276 51 85 0 94 0 4 173 335 0 0 100
3 246 43 107K 3932 14K 4 0 0 0 0 0 12 98 330 0 0 100

uptime -m
12:00 up 34 days, 14:01, 1 user, Mach factor: 0.00, 0.02, 0.00

Why is the Mach factor almost 0? There is no significant system activity. I do not see any problem?

I have verified the error logger:

tail /var/log/messages

evmwatch |evmshow &

cd /var/adm/syslog.dated/current

ls -lrt

tail ...

[Martin Moore]

What do you get for load average? Can you post the output of just "uptime" (with no -m)?

Martin

[Ivan Ferreira]

Hi Geert. I must recognize that your question is totally new for me. I've been working with tru64 since the 4.0D and never used the "Mach Factor" as a performance indicator. In fact, is the first time that I hear about it, and searching for information, found almost nothing.

[Geert Van Pamel]

The Mach factor is the amount of idle CPU on a server.

It is a decimal fraction between 0 (running at maximum capacity) and 1 (completely idle).

Now I get the following values:

uptime
14:49 up 34 days, 16:50, 1 user, load average: 0.00, 0.01, 0.00

uptime -m
14:50 up 34 days, 16:50, 1 user, Mach factor: 0.80, 0.79, 0.77

The Mach factor is higher now (as compaired with the values above) but should be much closer to 1 since the system is nearly completely idle.

[Martin Moore]

For curiosity, I checked several systems that I have access to, and my conclusion is that Mach factor should approach 1 *per CPU* on a lightly loaded system. Does your DS20 have only one CPU?

However, none of the systems I can access is running V5.1, so it's possible that something has changed in the kernel's calculation of Mach factor. There doesn't seem to be much on it; as far as I can tell, most people look at load average rather than Mach factor.

Martin