I have this problem as well on Cinnamon, so it doesn't appear to be specific to KDE. It stalls often and frequently over 15-30 seconds at a time for no apparent reason. But the swapping to disk may be a clue.
I see this on 5.4.0-40 and have also tried with the lowlatency version of the kernel and it doesn't help. One thing that seems to reduce the frequency of the problem somewhat is to disable transparent_hugepage support but it still happens even after that. I have 32GB ram and it starts happening when I get to about 50% ram (mem available) usage. The system also appears to start swapping at that point despite what swappiness is set to. I tried setting it to 10 but it is still swapping at what appears to be ~ 50% usage. It appears to be very easy to reproduce if you run a few VMware VMs on a system. # cat /proc/sys/vm/swappiness 10 $ free -m total used free shared buff/cache available Mem: 31030 6591 246 9050 24192 14936 Swap: 32767 4942 27825 $ cat /proc/meminfo MemTotal: 31774792 kB MemFree: 256768 kB MemAvailable: 15324804 kB Buffers: 5887324 kB Cached: 16712984 kB SwapCached: 488276 kB Active: 19816476 kB Inactive: 8835508 kB Active(anon): 12801324 kB Inactive(anon): 2522936 kB Active(file): 7015152 kB Inactive(file): 6312572 kB Unevictable: 145612 kB Mlocked: 48 kB SwapTotal: 33554428 kB SwapFree: 28493052 kB Dirty: 2301336 kB Writeback: 9564 kB AnonPages: 6161528 kB Mapped: 7931416 kB Shmem: 9272240 kB KReclaimable: 2201904 kB Slab: 2451272 kB SReclaimable: 2201904 kB SUnreclaim: 249368 kB KernelStack: 21552 kB PageTables: 85272 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 49441824 kB Committed_AS: 30098296 kB VmallocTotal: 34359738367 kB VmallocUsed: 55400 kB VmallocChunk: 0 kB Percpu: 7712 kB HardwareCorrupted: 0 kB AnonHugePages: 0 kB ShmemHugePages: 0 kB ShmemPmdMapped: 0 kB FileHugePages: 0 kB FilePmdMapped: 0 kB CmaTotal: 0 kB CmaFree: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 0 kB DirectMap4k: 5078656 kB DirectMap2M: 27346944 kB DirectMap1G: 0 kB ** Changed in: linux (Ubuntu) Status: Invalid => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1852001 Title: KDE GUI freeze on high disk IO To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1852001/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs