Odd Firefox issue - time gaps in tests

Web Performance Discuss Test Results
1

Hello All,

Apologies if this is not the right forum for it. If it’s not, please point me in the right direction.

I have a niggly situation with Firefox (various ESR versions - 22 and 24 mostly) - what sometimes happen with Firefox is that we intermittently have a gap in test result timings of up to 15 seconds. This does not happen frequently, one would be lucky to see this between 1%-10% of all tests done. Still, it is noticeable. Our tests were also done in a relatively well controlled environment where we do static page downloads from a dedicated server in a scheduled fashion, although this happens across the Internet so that we can “simulate reality” after a fashion. This particular issue does not happen with IE8/9/10 or Chrome, so it could possibly be indicative of a bug in FF. We have managed to isolate the behaviour to processes within FF, since packet captures with Wireshark proved that network latency wasn’t a factor. Using the Win7 process monitor we could see that FF is literally doing nothing.

Have anyone else spotted this type of behaviour at all? If so, please let me know! If there is indeed an issue, it would be easier to convince Mozilla devs that there is indeed a problem if this is a shared experience.

Thanks in advance!

Regards,
Jan Henkins

2

We eventually tracked this down to the Flash plugin crashing, Firefox’s crash reporter pops up, wptdriver closes it down and then there seems to be no network traffic from FF for 15 - 20 seconds.

To fix we disabled the crash reporter, and set a Flash config var as follows:

  1. Adding the system environment variable MOZ_CRASHREPORTER_DISABLE=1
  2. Adding the line ProtectedMode=0 to c:\windows\system32\macromed\flash\mms.cfg.

Other ways of disabling it are listed here: Mozilla Crash Reporter - MozillaZine Knowledge Base