[ProgClub programming] top: st : time stolen from this vm by the hypervisor

Jedd Rashbrooke jedd.rashbrooke at gmail.com
Thu Jun 6 16:42:49 AEST 2019


On Thu, 6 Jun 2019 at 16:18, Roland Turner via programming <
programming at progclub.org> wrote:

> This is akin to replacing token-passing with CSMA/CD.
>

 Yes.  I'm a big fan.

 I suggest a robust bash function could be rattled up with little effort
(albeit for even less point).


> It will work of course, but is rather more complicated because of the need
> to perform recovery, including random backoffs. Granted, in a likely case
> (backups), it probably isn't a disaster for both to simply fail and not
> bother with recovery at all. I'd suggest that where mkdir or flock are
> available, they're better choices.
>

 Backoffs are vanishingly unlikely - and require a second instance to be
run in the time it takes the first to evaluate 'ls dir/path/flag.* | grep
-v dir/path/flag.$$' and then 'touch dir/path/flag.$$'

 So, handle it, certainly, but at that point I'd raise an error, and
investigate it - mostly out of mild curiosity - when it happens once every
27,000 years.

 Since we're agreed that exceptions should alert a human, who can either
troubleshoot and re-engineer, or not, I'd abort on any case, and forget
about automated recovery etc.  (Much as per the current situation, but with
less staring.)

> The Blue Mountains have relocated to Galapagos?
>
> https://en.wikipedia.org/wiki/Turtles_all_the_way_down

 j.
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