On 2015-11-14 04:28, Todd C. Miller wrote:
> On Fri, 13 Nov 2015 16:45:44 -0700, Theo de Raadt wrote:
>
>>> This patch changes the default setting to 1.5 *
>>> (number_of_cpus_in_system) instead, which I find better matches modern
>>> behaviour.
>>
>> A larger number is sensible in this position.
>>
>> I would propose 8. I don't agree with a calculation like that; the
>> amount of work a system can do should not be calculated like that.
>
> I think 8 is way to high. Isn't the point of batch to run things
> when the machine is mostly idle?
The problem is (and we've had this discussion several times before at
least in misc@), that the system load doesn't really tell us that.
It *may* be the case that the system is under lots of work, but it may
also be the case that there are many processes just blocking waiting for
some resource and that the system is essentially idling.
My particular problem, and the reason I suggested this patch in the
first place, is that I often see loads of 20-30-50 or even way more,
without there even being a problem. The machine is very responsive, and
everything works great - there are just a lot of processes running or
waiting for an opportunity to run.
Since the system load essentially is a decaying average of the number of
runnable or running processes, it is not in any way connected to actual
processor workload as in instructions executed, just to the fact that
there is much *potentially* going on in the system.
For example, I run a couple of Hadoop clusters (not on OpenBSD
unfortunately), and with cluster nodes containing dual 6-core
hyper-threading Xeon processors, there is 24 "cores" that can be tasked
with calculations, and if they are all doing something the system load
will be at least 24 - but there would be no problem whatsoever to do
more things on the server, especially since the map/reduce tasks are
running with lowered priority. Each core's individual load would be about 1.
That's also why I suggested to base the default on a value relative to
the number of cores - it made sense from my practical point of view. But
I understand where Theo's coming from on this.
Regards,
/Benny
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