Benchmarking Mercury As The "Fastest Firefox Fork" With AVX, AES, LTO + PGO

Following the news last week of Firefox outperforming Chrome in SunSpider, a Phoronix reader pointed out Mercury that is an open-source web browser claiming to be the "fastest Firefox fork" and making use of Advanced Vector Extensions (AVX) and AES instructions along with compiler features like Link-Time Optimizations (LTO) and Profile-Guided Optimizations (PGO). The project advertises as being 8-20% faster than upstream Firefox. Curious I ran a couple benchmarks on my end of this Firefox fork.

Via the thorium.rocks project site is more information on the Firefox fork as well as Thorium as its similar optimized version of Google Chromium (benchmarks there in a separate article). Mercury does also pull in patches from other forks like LibreWolf, Waterfox, PlasmaFox, and GNU IceCat. Mercury also details its patches for how it goes about this optimized build.

Their 8% to 20% performance boost over the upstream "vanilla" Firefox is documented here with benchmarks such as Speedometer, Octane, and JetStream 2.

Curious about the performance myself and to complement the Firefox beta vs. Chrome benchmarks I carried out last week, I ran some Firefox/Mercury benchmarks again on the AMD Ryzen 9 7950X test bed with Ubuntu Linux. The stock Linux x86_64 packages from Mozilla were used as usual as well as the official Mercury Linux x86_64 build. The versions for this comparison included:

- Firefox 115.0.2
- Firefox 116.0.3
- Firefox 117.0b8
- Firefox 118.0a1
- Mercury 115.0.2

Mercury 115 was the newest version as of testing time plus tossing in the newer versions of Firefox for reference. The CPU power consumption and CPU usage were also monitored while benchmarking these Linux 64-bit web browsers in various common web benchmarks.