On 19 December 2015 at 20:02, <ele...@gmail.com> wrote:
>
>> As can be seen, all the 8 cores of my pc is being used by the julia
>> program, however, only 35% of the system resource is covered. My julia code
>> mainly does the fft operates in a loop. I use fftw.set_num_threads(8)
>> outside the loop. In my opinion, the top command should exhibit nearly 100%
>> use of the system resource, but that's not true.
>
> I'm not quite sure where you get 35% from, as I read your `top` the top
> three users are Julia using 6.89 cpus, QQ.exe 0.45 cpu and X 0.11 cpu.
> Julia is getting the vast majority of the cpu resources, nearly 7 out of 8
> cores.
He is reading time spent in user space which is given as 35.0%, the
problem however is that 60.6% of the time is spent on kernel processes
which is a really bad sign. Without seeing the code it is difficult
to know what is going on, especially since I am not familiar with
FFTW. My best guess is that the job is I/O bound or that the data
given to FFTW is so small that the thread overhead is eating up
performance. For the latter, set the number of threads to one and see
if the performance improves.
Pontus
