Just for perspective on this, I've used Linux since about 1993 (originally Slackware, then Gentoo, then Ubuntu) and recall manually adding irqtune to my system in the distant past.
When irqtune was originally developed, it was common to run XT-PIC, all interrupts were went to CPU 0, period. When one turned on IO-APIC back then, interrupts still went to CPU 0 by default but could be rerouted. This was largely to be able to hit gigabit+ speeds on systems of the time. Now? CPUs are faster, memory is faster, and the interrupt handlers are much more efficient than in the kernel of, say, 15 or 20 years ago. If you disable irqtune, you can observe in /proc/interrupts that various device interrupts are still sent to CPUs other than CPU0, they just don't go ping-ponging around between all of them like they do with irqtune. A big difference compared to the early days, for example for ethernet a lot of the work that was done in the interrupt handler back then, the interrupt handler now does the bare minimum and does the rest of the work with a kernel thread (same for wifi, which tends to be a bit of an interrupt and CPU hog). Meaning the actual interrupts take much less time to run now than they did then. The total CPU time could still add up to more than 1 core can handle if you had, say, 10gbps ethernet (or 1gbps ethernet or wifi on a slower CPU). But the kernel threads can be scheduled to any CPU core just like any other thread even if the interrupts are tied to one CPU.. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to ubuntu-meta in Ubuntu. https://bugs.launchpad.net/bugs/1833322 Title: Please consider no more having irqbalance enabled by default (per image/use-case/TBD) Status in Ubuntu on IBM z Systems: Confirmed Status in irqbalance package in Ubuntu: Confirmed Status in ubuntu-meta package in Ubuntu: Confirmed Bug description: as per https://github.com/pop-os/default-settings/issues/60 Distribution (run cat /etc/os-release): $ cat /etc/os-release NAME="Pop!_OS" VERSION="19.04" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Pop!_OS 19.04" VERSION_ID="19.04" HOME_URL="https://system76.com/pop"; SUPPORT_URL="http://support.system76.com"; BUG_REPORT_URL="https://github.com/pop-os/pop/issues"; PRIVACY_POLICY_URL="https://system76.com/privacy"; VERSION_CODENAME=disco UBUNTU_CODENAME=disco Related Application and/or Package Version (run apt policy $PACKAGE NAME): $ apt policy irqbalance irqbalance: Installed: 1.5.0-3ubuntu1 Candidate: 1.5.0-3ubuntu1 Version table: *** 1.5.0-3ubuntu1 500 500 http://us.archive.ubuntu.com/ubuntu disco/main amd64 Packages 100 /var/lib/dpkg/status $ apt rdepends irqbalance irqbalance Reverse Depends: Recommends: ubuntu-standard gce-compute-image-packages Issue/Bug Description: as per konkor/cpufreq#48 and http://konkor.github.io/cpufreq/faq/#irqbalance-detected irqbalance is technically not needed on desktop systems (supposedly it is mainly for servers), and may actually reduce performance and power savings. It appears to provide benefits only to server environments that have relatively-constant loading. If it is truly a server- oriented package, then it shouldn't be installed by default on a desktop/laptop system and shouldn't be included in desktop OS images. Steps to reproduce (if you know): This is potentially an issue with all default installs. Expected behavior: n/a Other Notes: I can safely remove it via "sudo apt purge irqbalance" without any apparent adverse side-effects. If someone is running a situation where they need it, then they always have the option of installing it from the repositories. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1833322/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
