On 22 Feb 2015 at 19:43:08, Aaron Hardy at AC ([email protected](mailto:[email protected])) wrote:

Hi Vincent,

Thanks for the follow-up.

I never managed to track down the exact cause of the futex lock or gettimeofday calls. My best guess is that it has something to do with XWiki running on an Amazon EC2 instance. I didn't see the same kind of issues on a local machine. I had another thread a few months ago where I asked if anyone had successfully run XWiki on AWS, and it didn't seem like there was much experience with that setup.

My short term solution was just to double the RAM and throw it all at XWiki. That seems to have mostly dealt with the stability issues (at least, the instance rarely crashes under load), but under the hood I think it's still performing much worse than it should be.

Any ideas you have about what might be causing the issue, or any tips for running XWiki on Amazon under reasonably high loads would be much appreciated. 

Thanks for the information and indeed you could be right about the Amazon EC2 context for the futex problem. I don’t have any experience with running XWiki on Amazon EC2 so I cannot help much, sorry. Thanks -Vincent

Thanks,

aaron

On Fri, Feb 20, 2015 at 10:05 AM, [email protected](mailto:[email protected]) wrote:

...

Hi Aaron,

Sorry you didn’t get any answer…

Were you able to find out the problem and improve XWiki under load?

Thanks -Vincent

On 20 Sep 2014 at 06:52:10, Aaron Hardy at AC ([email protected](mailto:[email protected])(mailto:[email protected])) wrote:

...

Trying to track down the source of some persistent performance issues under load with 6.2 RC 1 (haven't had time to upgrade to 6.2 final yet). I'm maxing out at about 30 or so users before dying on a system with 4GB of RAM.

The java interpreter is getting pegged to 100% of the CPU, and about 70% of the calls in the stack trace are futex lock errors. A good chunk of the remainder are gettimeofday calls.

Potentially useful info (sorry for formatting):

% time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 72.75 5361.592109 45075 118947 14045 futex 12.28 905.064191 466 1943354 gettimeofday 4.83 356.110745 3709487 96 45 restart_syscall 2.88 212.173358 836 253729 clock_gettime 2.71 199.867690 8802 22706 recvfrom 2.10 154.843342 37841 4092 poll 1.14 84.282371 580 145307 130153 stat

Any ideas?

thanks,

aaron