Hi! > >> Abstract > >> ======== > >> > >> The modern servers allows multiple cores to run at range of frequencies > >> higher than rated range of frequencies. But the power budget of the system > >> inhibits sustaining these higher frequencies for longer durations. > > > > Thermal budget? > > Right, it is a good point, and there can be possibility of Thermal throttling > which is not covered here. > But the thermal throttling is less often seen in the servers than the > throttling > due to the Power budget constraints. Also one can change the power cap which > leads > to increase in the throttling and task packing can handle in such > cases.
Ok. I thought you are doing this due to thermals. If I understand
things correctly, you can go over thermal limits for a few seconds
before the silicon heats up. What is the timescale for power budget?
> BTW, Task packing allows few more cores to remain idle for longer time, so
> shouldn't this decrease thermal throttles upto certain extent?
I guess so, yes.
> > >> These numbers are w.r.t. `turbo_bench.c` multi-threaded test benchmark
> >> which can create two kinds of tasks: CPU bound (High Utilization) and
> >> Jitters (Low Utilization). N in X-axis represents N-CPU bound and N-Jitter
> >> tasks spawned.
> >
> > Ok, so you have description how it causes 13% improvements. Do you also
> > have metrics how
> > it harms performance.. how much delay is added to unimportant tasks etc...?
> >
>
> Yes, if we try to pack the tasks despite of no frequency throttling, we see a
> regression
> around 5%. For instance, in the synthetic benchmark I used to show
> performance benefit,
> for lower count of CPU intensive threads (N=2) there is -5% performance drop.
>
> Talking about the delay added to an unimportant tasks, the result can be
> lower throughput
> or higher latency for such tasks.
Thanks. I believe it would be good to mention disadvantages in the
documentation, too.
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
signature.asc
Description: Digital signature
