Why is Firefox slower on Linux than Windows?

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Have you tried Firefox 4 on Linux and then tried Firefox on a friend’s Windows 7 PC? The experience isn’t the same and that’s not good news for Linux users.

Mozilla is apparently aware of the issue and they are taking steps to improve Firefox 4’s performance on Linux.

“We finally managed to get our Linux (and, obviously, Linux64) builds to
use GCC 4.5, with aggressive optimization (-O3) and profile guided
optimization enabled,” Mozilla developer Mike Hommey blogged. “This means we are finally using a more modern
toolchain, opening opportunities for things such as static analysis.
This also means we are now producing a faster Firefox, now much closer
to the Windows builds on the same hardware on various performance tests.”

The bad news is that the GCC 4.5 optimization aren’t likely to land on the mainline until Firefox 6. Though with Mozilla new aggressively agile development path, Firefox 6 is likely to be released this year.

Still, the whole issue begs the question of why Linux isn’t a bigger priority for Mozilla.

I’ve spoken with Mozilla staffers about Linux at multiple points over the last several years as issues of whether or not Mozilla cares about Linux have popped up. Long story short is that Mozilla does care about Linux and have since the beginning of Mozilla itself.