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Comments (45)

• glyco
  The new design is still wrong though - the swap system is a cache, there's no reason why a page should only exist on one level.
• hackernudes
  I see some comments about soft lockups during memory pressure. I have struggled with this immensely over the years. I wrote a userspace memory reclaimer daemon and have not had a lockup since: https://gist.github.com/EBADBEEF/f168458028f684a91148f4d3e79... .The hangs usually happened when I was stressing VFS (the computer was a samba server) along with other workloads. To trigger a hang manually I would read in large files (bigger than available ram) in parallel while running a game. I could get it to hang even with 128GB ram. I tweaked all the vfs settings (swappiness, etc...) to no avail. I tried with and without swap.In the end it looked like memory was not getting reclaimed fast enough, like linux would wait too long to start reclaiming memory and some critical process would get stuck waiting for some memory. The system would hang for minutes or hours at a time only making the tiniest of progress between reclaims.If I caught the problem early enough (just as everything started stuttering) I could trigger a reclaim manually by writing to '/sys/fs/cgroup/memory.reclaim' and the system would recover. I wonder if it was specific to btrfs or some specific workload pattern but I was never able to figure it out.
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  Numerlor
  The swap/memory situation in linux has surprised me quite a bit coming from Windows.Windows remains mostly fully responsive even when memory is being pushed to the limits and swapping gigabytes per second, while on linux when I ran a stress test that ate all the memory I had trouble even terminating the script
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  robinsonb5
  OOM killers serve a purpose but - for a desktop OS - they're missing the point.In a sane world the user would decide which application to shut down, not the OS; the user would click the appropriate application's close gadget, and the user interface would remain responsive enough for that to happen in a matter of seconds rather than minutes.I understand the many reasons why that's not possible, but it's a huge failing of Linux as a desktop OS, and OOM killers are picking around the edges of the problem, not addressing it head-on.(Which isn't to say, of course, that OOM killers aren't the right approach in a server context.)
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  ChocolateGod
  Is there a reason as to why Linux has not adopted straight up page compression like Windows and macOS?
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  anthk
  OpenBSD and the rest have a limits file where you can set RAM limits per user and sometimes per process, so is not a big issue.On GNU/Linux and the rest not supporting dynamic swap files, you can swap into anything ensembling a file, even into virtual disk images.Also set up ZRAM as soon as possible. 1/3 of the physical RAM for ZRAM it's perfect, it will almost double your effective RAM size with ease.