In the first days spent developing the CI tests for our Vagrant images, I used the Jenkins web interface a lot, without ever closing the tab or the browser. At the end of the second day, my Mac mini became very slow - I found it using 970MB of swap, and the Firefox process' memory had grown from the typical 700-900MB to 2.95GB. Firefox' about:memory reported that ci.centos.org took 1.6GB, out of which 1.2GB in 'orphan DOM nodes'.

Someone from #memshrink on irc.mozilla.org told me that a fix for something related to Jenkins had been committed in the past week, and I should try to reproduce it with Firefox Nightly. I used a clean profile, only loaded ci.centos.org and left it alone, without doing anything. Over 7 hours, the memory usage of the web content process increased from 122MB to 1.78GB. I also tried this evening with Firefox 48.0.2 from Fedora 24, with a fresh profile: the memory usage increased from 192MB to 613MB in 60 minutes (305MB being 'orphan DOM nodes', according to about:memory). I was also able to reproduce this behavior with Safari and Chrome on OS X: Safari went from 67MB to 1GB, while Chrome went from 120MB to 1.7GB, both in less than 3 hours.

This looks like a bug in the Jenkins web interface. Unfortunately, I had already filed a bug with Mozilla [1] before finding a bug report from January 2014 in the Jenkins tracker, describing a memory leak in Chrome, Firefox and Internet Explorer (all running on Windows). [2]

Is there anyone with a good understanding of closures and cyclic references between Javascript objects and the DOM, willing to take a look at what's going on? The Developer Tools in both Firefox and Chrome are able to take heap snapshots and compare them, and also record all memory allocations; this would probably make debugging easier than it was the case in January 2014.

Regards, Laurențiu

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1298981 [2] https://issues.jenkins-ci.org/browse/JENKINS-10912