[cmake-developers] CTest load balancing

[Wouter Klouwen]

On 16/10/2019 15:10, Brad King wrote:
> On 10/16/19 10:05 AM, Wouter Klouwen wrote:
>> Is the intent for CTest to specifically manage CPU load or system load
>> overall?
>
> I don't think a careful distinction was made at the time.
>
> If Linux needs some updates to be consistent with other platforms
> then that would be fine with me.

Unfortunately this may be easier said than done.

Most of the data relevant to this lives in /proc. Indeed the
getloadavg() implementation of glibc merely reads /proc/loadavg*.

For load average the scheduler keeps track of the running 1, 5, 15
minute running averages.

There's /proc/stat which keeps a running total of the CPU usage - the
first lines beginning with `cpu` - but for the purposes of this it is in
the format of usage since boot. In order to replicate a CPU utilisation
only load, you'd effectively have to pick a point in time to start and
then measure since the reference point, which makes things a bit
complicated.

From the same file you could also take the lines `procs_running` and
`procs_blocked`, sum them and present them as a pseudo load. It would be
a fairly robust calculation. I don't know if this would be quite correct
though.

I might just create an issue for this.

   W


*:
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/getloadavg.c;hb=HEAD
th

>
> -Brad
>
>
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