RPI3 swap experiments (grace under pressure)

[Patrick Crilly]

On 14-Aug-18 11:42 AM, bob prohaska wrote:
> [Altered subject, philosophical question]
> On Mon, Aug 13, 2018 at 01:05:38PM -0700, Mark Millard wrote:
>> Here there is architecture choice and goals/primary
>> contexts. FreeBSD is never likely to primarily target
>> anything with a workload like buildworld buildkernel
>> on hardware like rpi3's and rpi2 V1.1's and
>> Pine64+ 2GB's and so on.
>>
> I understand that the RPi isn't a primary platform for FreeBSD.
> But, decent performance under overload seems like a universal
> problem that's always worth solving, whether for a computer or
> an office. The exact goals might vary, but coping with too much
> to do and not enough to do it with is humanity's oldest puzzle.

It's a very difficult problem to solve.  And provokes some pretty heated 
arguments.

If you are experiencing overload, then there's a case for saying the 
platform/system isup to the task.
>   
> Maybe I should ask what the goals of the OOMA process serve.
> I always thought an OS's goals were along the lines of:
> 1. maintain control
> 2. get the work done
> 3. remain responsive
>
> There's at least some degree of conflict between all of them,
> made worse when the workload grows beyond the design assumptions.
> The RPI makes the issue more visible, but it's always lurking.
>
> OOMA seems to sacrifice getting work done, potentially entirely,
> in support of keeping the system responsive and under control.

I believe the thinking is that if the system remains remains responsive 
you have a chance of fixing the problem or at the very least you can 
login and gather information about what is causing the problem.

>
> To have some fun with the office analogy, when business is
> slow the clerk serves customers as they come in. When things
> get busy, the clerk says "take a number". When they get really
> busy new customers are told "come back tomorrow" and when they
> get absolutely frantic present customers are told "I can't finish
> this now, I'll call you when it's done". That's grace under pressure.

Nice analogy. If people just keep coming all day, I think what you've 
described is a responsive system. The clerk isn't getting any work 
done,  he's just responding to customers.  And would "can't finish it 
now" be analogous to killing  off processes?
> What do FreeBSD's designers want the system to do as it's
> progressively overworked? Is the office analogy too ambitious?
>
> Thanks for reading, and apologies for the ruminating.
>

-- 
"With great power comes great electricity bill"