server January 2020

server@lists.fedoraproject.org

3 participants
3 discussions

OOM managers, resource control
by Chris Murphy 21 Jan '20

21 Jan '20

Hi, Workstation working group continues to evaluate oom managers and seek input from domain experts on the subject. I've come across this video from the All Systems Go conference, on the larger subject of resource control. Its server+cloud+container oriented. So I think it speaks directly to your use cases. Resource Control (2019) Dan Schatzberg https://www.youtube.com/watch?v=30i7SamZxRU I'm looking into setting up a discussion session with Dan, and do some Q&A. I'll report back when I know more about that. -- Chris Murphy

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earlyoom by default
by Chris Murphy 13 Jan '20

13 Jan '20

Hi server@ and cloud@ folks, There is a system-wide change to enable earlyoom by default on Fedora Workstation. It came up in today's Workstation working group meeting that I should give you folks a heads up about opting into this change. Proposal https://fedoraproject.org/wiki/Changes/EnableEarlyoom Devel@ discussion https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org… The main issue on a workstation, heavy swap leading to an unresponsive system, is perhaps not as immediately frustrating on a server. But the consequences of indefinite hang or the kernel oom-killer triggering, which is a SIGKILL, are perhaps worse. On the plus side, earlyoom is easy to understand, and its first attempt is a SIGTERM rather than SIGKILL. It uses oom_score, same as kernel oom-killer, to determine the victim. The SIGTERM is issued to the process with the highest oom_score only if both memory and swap reach 10% free. And SIGKILL is issued to the process with the highest oom_score once memory and swap reach 5% free. Those percentages can be tweaked, but the KILL percentage is always 1/2 of the TERM percentage, so it's a bit rudimentary. One small concern I have is, what if there's no swap? That's probably uncommon for servers, but I'm not sure about cloud. But in this case, SIGTERM happens at 10% of RAM, which leaves a lot of memory on the table, and for a server with significant resources it's probably too high. What about 4%? Maybe still too high? One option I'm thinking of is a systemd conditional that would not run earlyoom on systems without a swap device, which would leave these systems no worse off than they are right now. [i.e. they eventually recover (?), indefinitely hang (likely), or oom-killer finally kills something (less likely).] I've been testing earlyoom, nohang, and the kernel oom-killer for > 6 months now, and I think it would be completely sane for Server and Cloud products to enable earlyoom by default for fc32, while evaluating other solutions that can be more server oriented (e.g. nohang, oomd, possibly others) for fc33/fc34. What is clear: this isn't going to be solved by kernel folks, the kernel oom-killer only cares about keeping the kernel alive, it doesn't care about user space at all. In the cases where this becomes a problem, either the kernel hangs indefinitely or does SIGKILL for your database or whatever is eating up resources. Whereas at least earlyoom's first attempt is a SIGTERM so it has a chance of gracefully quitting. There are some concerns, those are in the devel@ thread, and I expect they'll be adequately addressed or the feature will not pass the FESCo vote. But as a short term solution while evaluating more sophisticated solutions, I think this is a good call so I thought I'd just mention it, in case you folks want to be included in the change. -- Chris Murphy

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Cockpit 210 and Cockpit-podman 12
by Katerina Koukiou 09 Jan '20

09 Jan '20

Cockpit is the modern Linux admin interface. We release regularly. Here are the release notes from version 210: https://cockpit-project.org/blog/cockpit-210.html Summary: - Overview: Add CPU utilization to usage card - Dashboard: Support SSH identity unlocking when adding new machines - SElinux: Introduce an Ansible automation script - Machines: Support bridge type network interfaces - Machines: Support bus type disk configuration You can get Cockpit here: http://cockpit-project.org/running.html Cockpit 210 is available in Fedora 30: https://bodhi.fedoraproject.org/updates/FEDORA-2020-8ff69018de And Fedora 31: https://bodhi.fedoraproject.org/updates/FEDORA-2020-afa121b867 Or download the tarball here: https://github.com/cockpit-project/cockpit/releases/tag/210 Cockpit-podman also had a release! It now supports configuration of CPU shares for system containers. The release notes from version 12 are bundled with Cockpit's release notes. Cockpit-podman 12 is available in Fedora 30: https://bodhi.fedoraproject.org/updates/FEDORA-2020-63b7f0d62a And Fedora 31: https://bodhi.fedoraproject.org/updates/FEDORA-2020-fbffc4a3a3 Or download the tarball here: https://github.com/cockpit-project/cockpit-podman/releases/tag/12 Kind regards, Katerina

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server January 2020