"Retbleed Fix Slugs Linux VM Performance by up to 70 Percent"

VMware engineers tested the Linux kernel's fix for the Retbleed speculative execution bug and discovered that it can reduce computing performance by up to 70 percent. VMware performance engineering staffer Manikandan Jagatheesan reports that running Linux VMs on the ESXi hypervisor using version 5.19 of the Linux kernel saw computing performance drop by up to 70 percent when using a single vCPU, networking performance drop by 30 percent, and storage performance drop by up to 13 percent. According to Jagatheesan, VMware's testers disabled the Retbleed remediation in kernel version 5.19, and ESXi performance returned to pre-version 5.18 levels. Disabling speculative execution has an impact on performance. A 70 percent decrease in computing performance will have a significant impact on application performance, potentially resulting in unacceptable delays for some business processes. VMware's tests were carried out on Intel Skylake CPUs, which were released between 2015 and 2017 and are still in use in many server fleets. Following CPU generations addressed the underlying issues that enabled Retbleed and other Spectre-like attacks. However, many VMware users will most likely have Skylake CPUs in production or unintentionally use them in clouds. Assuming those users have installed kernel version 5.19, which is unlikely, they have a choice. This article continues to discuss the findings from VMware engineers' testing of the Linux kernel's fix for the Retbleed speculative execution bug. 

The Register reports "Retbleed Fix Slugs Linux VM Performance by up to 70 Percent"