UPDATE: Microsoft has admitted the latest Windows 10 update that included the Retpoline CPU performance enhancement could have a negative impact on gaming performance.
Users have complained of frame rate hitches, lag spikes and low frame rates since installing the patch. Games affected so far include Destiny 2 and Call of Duty: Modern Warfare 2, among others.
“After installing KB4482887, users may notice graphics and mouse performance degradation with desktop gaming when playing certain games (eg: Destiny 2)," said Microsoft in a new update.
Microsoft says it is working on a solution but, in the meantime, the official recommendation is you uninstall the latest Windows update. “As a short-term resolution, users can uninstall KB4482887 to regain performance,” wrote Microsoft.
These botched updates are getting a bit embarrassing for Microsoft now. They've got plenty of time to test them through the Insider program so there's no way they should be arriving with obvious issues like this. Trust in Windows 10 is tenuous as it is and any good faith is being eroded with a series of buggy patches.
Original Story: 06-Mar-2019 - Windows 10 October 2018 Adds 'Retpoline' Fix That Greatly Reduces Spectre Performance Hit
The latest Windows 10 update KB4482887 (Build 17763.348) has taken aim at mitigating the performance impact of the Spectre CPU vulnerability, courtesy of the new ‘Retpoline’ Spectre variant 2 mitigation.
Spectre and Meltdown have largely been solved, at least on the security side of things, but the mitigations for these vulnerabilities also brought about a performance hit on the CPU. The performance hit varies depending on which CPU and OS you’re running, varying from negligible all the way up to 30% in edge cases. The Retpoline fix is designed to improve this performance hit and speed up CPUs.
Microsoft has said Retpoline will significantly improve the performance of the Spectre variant 2 mitigations for Windows 10. They claim 25% faster Office app launch times and 1.5-2x throughput in Diskspd (storage) and NTttcp (networking) benchmarks while using their test Broadwell processors.
Retpoline has been getting tested in the Insider build of Windows 10 for some time but is now generally available through the latest Windows 10 update. The new toggle is currently disabled by default but Retpoline can be manually enabled by adding various registry configuration updates. You can see more details on that here, but our advice is to hold fire until this gets officially enabled.
Created in conjunction with Google, Retpoline works by replacing all indirect call of jumps in kernel-mode binaries with an indirect branch sequence that has safe speculation behaviour.
It seems the name is short for ‘return trampoline’, creating what is effectively an infinite loop that is never executed by the CPU, therefore preventing the CPI from wasting time on any speculative execution. The finer details are well beyond my sphere of knowledge but the bottom line is it helps improve performance while the Spectre mitigations are in place.