On 03/20/2013 06:00 PM, Guido Seifert wrote: > > Hi, > I have here a strange problem. Probably not 100% ontopic for this list. But > it is a Qt program. :-) > > My problem: I have three programs, which exchange data with a fourth program > via tcp and udp. On my i7 and i5 with four cores it runs perfectly. It also > runs perfectly on my partner's machines. Now I gave it to a few testers... > and it was pure disaster. Bugs I have never seen before. From the description > it seems to be some kind of deadlock. The main program just freezes. None of > the four programs are multithreaded. At least not directly. The programs use > the Qt network classes. Since I don't have an unlimited pool of hardware I > tried to run my program in a Windows 7 and Windows 8 installation in a > VirtualBox environment. And strangely I could see exactly the reported > behaviour. But only when I gave the virtual machine< 4 cores. As soon as I > switched the virtual machine to four or more cores everything worked > perfectly again. Slow and jerky, but generally as expected. > > This behaviour is not 100% consitent. There is a tester with an i7 machine > and four cores, who sees the same blocking behaviour. > > I am a little at a loss here. Anyone of you seen something similar? Any ideas > what the problem could be? >
I don't suppose this problem correlates to the model name of the processor on which the programs are running. We had a freeze problem when a pair of processes tried to communicate over sockets on hardware which matched this (regex) model name: .*Xeon.*5[5-9][0-9][0-9].* The problem occurred with a low frequency and we spent a lot of time on it. The final solution was to insure that the appropriate threads of two applications which needed to communicate over a socket (on that hardware) were running on the same core. We did this by setting the cpu affinity. Bill > Guido > > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest > _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
