Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.debian.user > #274125

Re: Small server hanging after some days - top, load avg and Mem buff/cache question

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

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?

Back to linux.debian.user | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Small server hanging after some days - top,  load avg and Mem buff/cache question "B.M." <b-misc@gmx.ch> - 2024-10-28 11:50 +0100
  Re: Small server hanging after some days - top, load avg and Mem  buff/cache question "Alexander V. Makartsev" <avbetev@gmail.com> - 2024-10-28 12:40 +0100
  Re: Small server hanging after some days - top, load avg and Mem  buff/cache question Dan Ritter <dsr@randomstring.org> - 2024-10-28 15:40 +0100
    Re: Small server hanging after some days - top,  load avg and Mem buff/cache question "B.M." <b-misc@gmx.ch> - 2024-10-28 15:40 +0100
      Re: Small server hanging after some days - top, load avg and Mem  buff/cache question Dan Ritter <dsr@randomstring.org> - 2024-10-28 16:10 +0100

csiph-web