On Dec 7, 2014, at 11:06 PM, // ravi <[email protected]> wrote:
>
>
> I am stumped by what must clearly be a misreading on my part. Node 0.10 docs
> say that each element of os.cpus() contains information about each CPU/core.
> This information includes "the number of milliseconds the CPU/core spent in:
> user, nice, sys, idle, and irq” (the docs do not say milliseconds of what,
> but I assume it means milliseconds since the system was last started). Note
> that this used to be, in v0.8 (and I assume before), reported in CPU ticks,
> but seems to have switched to milliseconds for v0.10.
>
> Now for the puzzle: say I do this:
>
> console.log(os.cpus()[0].times.idle);
> setTimeout(function() { console.log(os.cpus()[0].times.idle); }, 2000);
>
> The output I see is:
>
> 39035126800
> 39035144500
>
> Assuming that ordering of CPUs/cores is consistent in the array returned by
> os.cpus(), it’s not clear how to square the above with the docs. The
> difference between the times reported is 17700ms i.e., CPU 0 was idle for 17
> seconds in the 2 seconds between the two calls!
>
One thing to consider is if os.cpus() returns CPU usage information from
/proc/stats. If so, two things could affect the above (more likely the second):
(1) the first line of /proc/stats in GNU/Linux reports the totals across CPUs.
(2) these numbers seem to be in “jiffies” or 1/100th of a second (USER_HZ).
Time to start digging into the ‘os’ module sources, I guess, though I think
Ockham’s Razor continues to point at me.
—ravi
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