The Firefox + Chrome Web Browser Performance Impact From Intel's JCC Erratum Microcode Update

With yesterday's overview and benchmarks of Intel's Jump Conditional Code Erratum one of the areas where the performance impact of the updated CPU microcode exceeding Intel's 0~4% guidance was on the web browser performance. Now with more time having passed, here are more web browser benchmarks on both Chrome and Firefox while comparing the new CPU microcode release for the JCC Erratum compared to the previous release. Simply moving to this new CPU microcode does represent a significant hit to the web browser performance.

In this article is just a look at how the updated CPU microcode for the JCC Erratum affects the Mozilla Firefox and Google Chrome web browser performance. This article isn't looking at any impact from the also new Zombieload TAA mitigation (that's coming in a separate article shortly) or anything else but simply benchmarking both of these web browsers with the old and new CPU microcode on a Skylake-X system.

Also differing from yesterday's article where Clear Linux was used was running the old/new CPU microcode on Ubuntu 19.10 with its default Linux 5.3 kernel.

While there is the JCC Erratum GNU Assembler optimizations to help offset the performance impact of the microcode change around jump instructions, it's not trivial recommending users recompile their web browsers for restoring lost performance -- particularly when that's not possible with Chrome itself (only Chromium), etc. Time will tell if Mozilla and Google will be quickly releasing new browser binaries built with Intel's patched assembler but at least for now moving to this new CPU microcode does represent a hit to the performance exceeding Intel's 4% guidance.

This updated CPU microcode is also already shipping on the likes of Ubuntu and other distributions in order to address this jump conditional code bug. See yesterday's aforelinked article for more details on this processor erratum affecting Skylake through Cascade Lake.

Now let's get to these fresh Firefox and Chrome benchmarks on Ubuntu 19.10 with the previous () and new () microcode. All benchmarks were carried out using the Phoronix Test Suite.