http://bugzilla.suse.com/show_bug.cgi?id=1120426 Bug ID: 1120426 Summary: Scramble btrfs maintenance timers (RandomizedDelaySec for btrfs-scrub.timer) Classification: openSUSE Product: openSUSE Distribution Version: Leap 15.0 Hardware: Other OS: Other Status: NEW Severity: Normal Priority: P5 - None Component: Basesystem Assignee: bnc-team-screening@forge.provo.novell.com Reporter: wagner-thomas@gmx.at QA Contact: qa-bugs@suse.de Found By: --- Blocker: --- I have an Leap 15.0 KVM host with many Leap 15.0 clients. All use btrfs as root filesystem. Some days round midnight, I experience a severe sluggishness of the system. Turns out, all VMs start their regular btrfs maintenance tasks via systemd timers at the same time, namely midnight. Although each VM starts the btrfs-{balance,trim,scrub} with low priority (IOSchedulingClass=idle, CPUSchedulingPolicy=idle), this does not consider that other VMs also started their btrfs maintenance tasks. This imposes a high load on the disks and all VMs are barely responsive. There is a systemd timer option RandomizedDelaySec. If this was set to like 1 day for btrfs-scrub.timer (runs every month) and like 12h for other btrfs task (they run every 5 days), the VMs would stagger their btrfs-maintenance task and not clog the disks. Maybe RandomizedDelaySec can be added to btrfs-{balance,trim,scrub}.timers -- You are receiving this mail because: You are on the CC list for the bug.