Retbleed Fix Slugs Linux VM Performance By Up To 70 Percent

VMware engineers have tested the Linux kernel's fix for the Retbleed speculative execution bug, and report it can impact compute performance by a whopping 70 percent. The Register reports: In a post to the Linux Kernel Mailing List titled "Performance Regression in Linux Kernel 5.19", VMware performance engineering staffer Manikandan Jagatheesan reports the virtualization giant's internal testing found that running Linux VMs on the ESXi hypervisor using version 5.19 of the Linux kernel saw compute performance dip by up to 70 percent when using single vCPU, networking fall by 30 percent and storage performance dip by up to 13 percent. Jagatheesan said VMware's testers turned off the Retbleed remediation in version 5.19 of the kernel and ESXi performance returned to levels experienced under version 5.18. Because speculative execution exists to speed processing, it is no surprise that disabling it impacts performance. A 70 percent decrease in computing performance will, however, have a major impact on application performance that could lead to unacceptable delays for some business processes. VMware's tests were run on Intel Skylake CPUs -- silicon released between 2015 and 2017 that will still be present in many server fleets. Subsequent CPUs addressed the underlying issues that allowed Retbleed and other Spectre-like attacks.

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