On Montag, 28. Oktober 2024 15:21:02 CET Dan Ritter wrote: > B.M. wrote: > > Hi, > > > > I have a small server (Raspberry Pi 4 in fact) and since a couple of weeks > > it repeatedly hangs after some days until I reboot it (after months of > > uptime without any problem - but I changed a few things in the meantime, > > so maybe load is now higher than before). > > > > At least after installing watchdog it reboots now automatically. > > > > Here some top output just before reboot: > > > > load avg 20 18 12 (so: much higher than normal, e.g. 1.1 1.2 1.5 or so) > > MiB Mem: 3835 total, 618 free, 1194 used, 2264 buff/cache > > MiB Swap: 1024 total, 600 free, 430 used, 2640 avail > > > > Processes with highest CPU usage: > > kswapd0 with 80% > > Swapping once is fine. Swapping continuously is bad. > > > java (openhab) 41% > > pg_dump 18% > > pg_dump should not be running continuously; if it is running too > long, you need a better way of backing up PG. Replication to > another server is usually very efficient. > > > Processes with highest Mem usage: > > java (i.e. openhab) with 626678 virt, 22% > > postgres 338824 virt > > postgre 338800 virt > > > > From my understanding, there is enough memory available, even swap usage > > wouldn't be necessary, since buff/cache is about 50% of physical memory. > > Is > > this correct? But than: why is it going to hang afterwards, or why this > > extreme load? > > > > The only swap device available is zram, no swap partition, no swap file. > > The system runs on btrfs > > Ooch. Your system is likely thrashing between using RAM for the > applications (java, PG, pg-dump) and using RAM to swap out from > RAM to compressed RAM (this does not buy you as much as you > think). > > The problem, then, is that you don't have enough RAM and you don't > have enough I/O speed to solve the RAM issue temporarily, so it > becomes permanent. > > Try disabling swap entirely. > > If that doesn't work, you need a machine with more RAM, or you > need to be using less RAM. > > -dsr- Thanks a lot for your inputs. In the meantime I disabled zram and added a 2 GiB swapfile. What I don't understand: how can the system have not enough memory problems, while it's showing ~ 2 GiB cached/buffer? I'd expect it to free some of that and be fine again... 2 GiB is about 50% of the physical RAM of 4 GiB?
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