Re: Severe performance degradation on Linux

On 05.01.2015 18:36, Maarten Hoes wrote:
> For what its worth, i can easily reproduce the script takes fairly long
> (about ~50 seconds on my vm's) to complete on both Ubuntu 14.04 and
> Fedora 21, both with the distro supplied binaries and a recent master.
>
> I ran the script using strace -f. It shows a lot of calls on futex(
> 'FUTEX_WAIT_PRIVATE'), though im not sure how relevant that may be. I
> attached the strace output.

please try that again and use strace options -T -r so it's easier to see
where the time is spent.


On Tue, Dec 30, 2014 at 01:58:00PM +0100, Markus Mohrhard wrote:
>    Hey,
>    You or we can now speculate for a long time or you can just start
>    profiling what is actually slow. Get a symbols build and run it with
>    callgrind. You can interpret the results with kcachegrind which will
>    hopefully show what took so much time and allow you to work on a fix.

this problem is probably not CPU bound, i'd guess something is waiting
for a time-out and callgrind's cycle-counting won't help much in that case.