The Good, the Blog & the Ugly - Tim Cook's Weblog

Margins in Consumer Telephony

Here is a little observation on telephone margins that is dear to my heart. Below is a list of rates (in US dollars per minute, taxes and other fees not shown) for various methods of calling from the US to a land-line in Australia. The last four options use VoIP.

As you may see, there is a 27000% range in these numbers. Even with that one carrier there is a 100x range. Plenty of opportunity for profit.

Hopefully it is useful to be aware there can be some very steep rates for ex-pat Aussies to call home if they are away from their preferred carrier.

I have been quite satisfied with CallWithUs, if anyone is interested. They even have a call-back feature if I want to call from my mobile.

While I'm on the topic, I should also mention this helpful message I got from my wireless (mobile) provider (although they are no longer my provider):

When you're on the go and don't have the info you need, AT&T 411 is here to help. Whether you're searching for a business or residence - dial 4-1-1 to get quick access to phone numbers and addresses. Plus, with AT&T 411 you can find movie times, driving directions and more. And it's just $1.79 per call plus standard airtime charges.*

Thanks for the reminder - I will be vigilant to avoid that $1.79 charge, and stick to 1-800-FREE411...

Posted at 02:35PM Feb 21, 2008 by timc in Personal  | 

Utilization - Can I Have More Accuracy Please?

Just thought I would share another Ruby script - this one takes the output of mpstat, and makes it more like the output of mpstat -a, only the values are floating point. I wrote it to process mpstat -a that I got from a customer. It can also cope with the date (in Unix ctime format) being prepended to every line. Here is some sample output:

CPUs minf mjf xcal  intr ithr  csw icsw migr smtx  srw syscl  usr sys  wt idl
 4 7.0 0.0 26.0 114.25 68.0 212.75 16.75 64.75 11.75 0.0 141.25 1.0 1.0 0.0 98.5
 4 0.75 0.0 929.75 2911.5 1954.75 10438.75 929.0 4282.0 715.0 0.0 6107.25 39.25 35.75 0.0 25.25
 4 0.0 0.0 892.25 2830.25 1910.5 10251.5 901.5 4210.0 694.5 0.0 5986.0 38.5 35.0 0.0 26.75
 4 0.0 0.0 941.5 2898.25 1926.75 10378.0 911.75 4258.0 698.0 0.0 6070.5 39.0 35.5 0.0 25.25
 4 0.0 0.0 893.75 2833.75 1917.75 10215.0 873.75 4196.25 715.25 0.0 5925.25 38.0 34.75 0.0 27.25

The script is here.

Interestingly, you can use this to get greater accuracy on things like USR and SYS than you would get if you just used vmstat, sar, iostat or mpstat -a. This depends on the number of CPUs you have in your system though.

Now, if you do not have a lot of CPUs, but still want greater accuracy, I have another trick. This works especially well if you are conducting an experiment and can run a command at the beginning and end of the experiment. This trick is based around the output of vmstat -s:

# vmstat -s
[...]
 54056444 user   cpu
 42914527 system cpu
1220364345 idle   cpu
        0 wait   cpu

Those numbers are "ticks" since the system booted. A tick is usually 0.01 seconds.

NEW: I have now uploaded a script that uses these statistics to track system-wide utilization.

Posted at 02:12PM Feb 13, 2008 by timc in Performance  |