[AndreasFrom]

Has anyone tested the difference between Mozilla's Firefox build and a local fully-optimized for your machine build? Or something similar with another piece of open source software. I wonder how much the "Gentoo-model" of compiling everything yourself affects everyday performance.

[kevingadd]

One big gap is that release builds of Firefox tend to have had profile-guided optimization applied, among other things, so you need to make sure you take steps like that correctly or your custom build will end up slower.

It's probably possible to produce a custom build for your machine that runs faster, whether by using custom instruction sets, or feeding different data to the optimizer when it's doing PGO. However, the risk you run there is that this could introduce bugs - Firefox and Chrome both regularly run into bugs caused by the optimizer or linker, and in some cases the fix is to stop the optimizer/linker from fiddling with that code.

[arbitrage]

In my experience, I was never able to get FF to work well on Gentoo; it always ran like a dog with three legs.

No matter what tweaks I tried, the binary builds from Moz always ran better.

[frozenport]

Everything on my Gentoo system runs faster than in the binary ebuild equivalent.

That being said, things like choosing the wrong preemption mode can introduce latency problems, etc. Most users experience higher throughput and higher latency when comparing Windows to Gentoo. I believe the higher user interface latency is the general case when going from Windows to Linux.