The choice was made from running analysis on a wide range of Intel machines, old and new. We are trying to select the optimal choice for a wide range of CPUs for a wide range of use cases. Generally speaking, the intel-pstate governor has deeper understanding of the processor features and can access CPU metrics that can guide it to making an informed choice.
>From our understanding, The intel-pstate driver should be the optimal choice for Intel Sandy Bridge CPUs onwards. The intel-pstate driver supports only the performance and powersave governors. In benchmarking we didn't observe much computational difference between the too once the CPU is fully loaded. However, cranking up or cranking down the load one will discover that the performance setting is more responsive than powersave. The overall compute throughput when fully loaded is the same, it's just a case that powersave may take a little longer to crank up to the full speed. It makes sense to default to powersave for most scenarios, especially for laptop users. Pre-Intel Sandy Bridge or non-x86 CPUs will default back to the non- intel pstate governor. So, question: Which kernel(s) are you referring to? -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1885730 Title: Bring back ondemand.service or switch kernel default governor for pstate - pstate now defaults to performance governor Status in linux package in Ubuntu: Confirmed Status in systemd package in Ubuntu: Invalid Status in linux source package in Groovy: Confirmed Status in systemd source package in Groovy: Invalid Bug description: In a recent merge from Debian we lost ondemand.service, meaning all CPUs now run in Turbo all the time when idle, which is clearly suboptimal. The discussion in bug 1806012 seems misleading, focusing on p-state vs other drivers, when in fact, the script actually set the default governor for the pstate driver on platforms that use pstate. Everything below only looks at systems that use pstate. pstate has two governors: performance and powerstate. performance runs CPU at maximum frequency constantly, and powersave can be configured using various energy profiles energy profiles: - performance - balanced performance - balanced power - power It defaults to balanced performance, I think, but I'm not sure. Whether performance governor is faster than powersave governor is not even clear. https://www.phoronix.com/scan.php?page=article&item=linux50-pstate- cpufreq&num=5 benchmarked them, but did not benchmark the individual energy profiles. For a desktop/laptop, the expected behavior is the powersave governor with balanced_performance on AC and balanced_power on battery. I don't know about servers or VMs, but the benchmark series seems to indicate it does not really matter much performance wise. I think most other distributions configure their kernels to use the powersave governor by default, whereas we configure it to use the performance governor and then switch it later in the boot to get the maximum performance during bootup. It's not clear to me that's actually useful. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1885730/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
