4 ms·

Not sure if equivalents are still recommended for Windows users, but I've seen zram recommended to Linux users quite a few times. Someone also wrote a script t

Not sure if equivalents are still recommended for Windows users, but I've seen zram recommended to Linux users quite a few times. Someone also wrote a script to start killing processes before the system can hang when it runs out of RAM. https://askubuntu.com/a/1018733 https://askubuntu.com/a/1018733

marginalia_nu 5y ago
> Someone also wrote a script to start killing processes before the system can hang when it runs out of RAM. Isn't this exactly what the OOMKiller does?
- themodelplumber 5y ago
  > does Makes you wonder... https://askubuntu.com/questions/1258371/oom-killer-never-runs https://askubuntu.com/questions/1258371/oom-killer-never-run...
  - marginalia_nu 5y ago
    I had a bunch of problems with the OOM Killer on a server of mine. It seems to have been due to not having any swap partition. Linux seems to assume you do, and the OOM strategy behaves really poorly when you don't. Like, it doesn't need to be large, the machine has 128 Gb RAM and the swap partition is 1 Gb.
    - aidenn0 5y ago
      1GB is a giant swap partition; linux regularly ran with swap partitions of 10s of MB in the 90s. The only reason to scale swap with ram is if you want to fit coredumps (or suspend to disk) in swap.
      - marginalia_nu 5y ago
        10s of Mb was a lot in the '90s though. A mid '90s consumer hard drive usually clocked in at a few hundred megabytes, and RAM could be in the dozens of Mb.
        aidenn0 5y ago
        Right, but swap size should scale with random access times for disks, not disk nor RAM size.
        marginalia_nu 5y ago
        Why is that?
- AceJohnny2 5y ago
  OOMKiller has a bunch of issues. Its heuristics don't apply well across the wide range of workloads Linux provides (mobile/android? webserver? Database server? build server? desktop client? Gaming machine?), each of which would require its own tuning. (more background at https://lwn.net/Kernel/Index/#Memory_management-Out-of-memory_handling https://lwn.net/Kernel/Index/#Memory_management-Out-of-memor...) That's why some orgs implemented their own solutions to avoid OOMKiller having to enter the picture, like Facebook's user-space oomd [1] or Android's LMKD [2] [1] https://github.com/facebookincubator/oomd https://github.com/facebookincubator/oomd [2] https://source.android.com/devices/tech/perf/lmkd https://source.android.com/devices/tech/perf/lmkd
- kmeisthax 5y ago
  In my experience, by the time the OOMKiller actually comes into play, the system has already stalled for minutes if not more. This especially applies to headless servers; good luck trying to SSH into a machine that keeps trying to launch a service configured to consume too much RAM.
5e92cb50239222b 5y ago
zram shouldn't really be recommended anymore, IMHO. zswap is the more modern alternative — it does not require a separate virtual device, can resize its pool dynamically, is enabled by default on some distributions, and (IIRC) supports more compression algorithms (trade CPU time for higher compression ration or vice versa). https://wiki.archlinux.org/title/Zswap https://wiki.archlinux.org/title/Zswap

marginalia_nu 5y ago

> Someone also wrote a script to start killing processes before the system can hang when it runs out of RAM. Isn't this exactly what the OOMKiller does?

themodelplumber 5y ago
> does Makes you wonder... https://askubuntu.com/questions/1258371/oom-killer-never-runs https://askubuntu.com/questions/1258371/oom-killer-never-run...
- marginalia_nu 5y ago
  I had a bunch of problems with the OOM Killer on a server of mine. It seems to have been due to not having any swap partition. Linux seems to assume you do, and the OOM strategy behaves really poorly when you don't. Like, it doesn't need to be large, the machine has 128 Gb RAM and the swap partition is 1 Gb.
  - aidenn0 5y ago
    1GB is a giant swap partition; linux regularly ran with swap partitions of 10s of MB in the 90s. The only reason to scale swap with ram is if you want to fit coredumps (or suspend to disk) in swap.
    - marginalia_nu 5y ago
      10s of Mb was a lot in the '90s though. A mid '90s consumer hard drive usually clocked in at a few hundred megabytes, and RAM could be in the dozens of Mb.
      - aidenn0 5y ago
        Right, but swap size should scale with random access times for disks, not disk nor RAM size.
        marginalia_nu 5y ago
        Why is that?
AceJohnny2 5y ago
OOMKiller has a bunch of issues. Its heuristics don't apply well across the wide range of workloads Linux provides (mobile/android? webserver? Database server? build server? desktop client? Gaming machine?), each of which would require its own tuning. (more background at https://lwn.net/Kernel/Index/#Memory_management-Out-of-memory_handling https://lwn.net/Kernel/Index/#Memory_management-Out-of-memor...) That's why some orgs implemented their own solutions to avoid OOMKiller having to enter the picture, like Facebook's user-space oomd [1] or Android's LMKD [2] [1] https://github.com/facebookincubator/oomd https://github.com/facebookincubator/oomd [2] https://source.android.com/devices/tech/perf/lmkd https://source.android.com/devices/tech/perf/lmkd
kmeisthax 5y ago
In my experience, by the time the OOMKiller actually comes into play, the system has already stalled for minutes if not more. This especially applies to headless servers; good luck trying to SSH into a machine that keeps trying to launch a service configured to consume too much RAM.

5e92cb50239222b 5y ago

zram shouldn't really be recommended anymore, IMHO. zswap is the more modern alternative — it does not require a separate virtual device, can resize its pool dynamically, is enabled by default on some distributions, and (IIRC) supports more compression algorithms (trade CPU time for higher compression ration or vice versa). https://wiki.archlinux.org/title/Zswap https://wiki.archlinux.org/title/Zswap