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Fix Firefox's memory problems, says Mozilla director

If there's a memory leak, it needs to be plugged before cell phone porting

November 12, 2007 12:00 PM ET

Computerworld - Mozilla Corp. must address Firefox's memory problems if it's serious about entering the mobile browser market, a member of the company's board of directors said over the weekend.

The on-again, off-again debate over whether Firefox has a memory leak was dragged back into the limelight by Christopher Blizzard, a Red Hat Inc. developer and longtime contributor to Firefox who also sits on Mozilla's board. "As Mozilla starts down the path to running in the mobile space, we are spending time looking at memory pressure issues more closely," Blizzard said in a posting to his personal blog on Saturday, referring to the leak that many users believe plagues Firefox.

The longer Firefox runs and more pages it opens, the theory goes, the larger its appetite for memory. At some point, the load is significant enough to hinder performance or in some cases, lock the browser. But closing tabs doesn't reclaim the memory; only shutting down the browser and restarting does.

Blizzard stopped short of calling the leak a feature, as other Firefox developers have in the past, but neither did he embrace the idea that one really exists. "It sounds like the early data suggests that Mozilla really doesn't leak that much memory at all," he said. "But it does thrash the [memory] allocator pretty hard and that's what causes the perception of memory leaks."

Even bringing up the idea of a memory leak was enough to bring out users who swore it was a reality, not just a perception. "I don't know if Mozilla actually leaks memory, but it's performance certainly degrades with use," said a user identified as sb in a comment to Blizzard's blog. "My browser is nice and snappy right at start-up, taking [a] 600MB footprint. After three days of intensive use, it's up to a 1.1GB footprint; no big deal, but it often locks up for multiple seconds."

According to tests run by another Firefox developer, Stuart Parmenter, the issue isn't so much an actual leak, but one of memory fragmentation, where large amounts of free memory are scattered between small blocks of used memory. "It makes it very difficult for us to get big chunks of contiguous memory to give back to the OS," said Parmenter. "This makes us look big."

Whether the leak is real and measurable or as Parmenter speculated, more fragmentation than a true leak, Blizzard tied work on the problem to Mozilla's move into the mobile market, which currently is dominated by Opera Software ASA's Opera Mini. Apple Inc., which this summer introduced a mobile edition of its Safari browser in the iPhone, and more recently, in the iPod Touch, would also be a mobile rival to Mozilla. "Over the next few months, it will be very interesting to see what happens with both memory usage and perceived performance, especially as we connect numbers to a successful mobile strategy," said Blizzard.



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