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Why is my server using all my Swap but I have RAM to spare? (lemmy.world)
submitted 1 year ago* (last edited 1 year ago) by to c/selfhosted@lemmy.world
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This is an old desktop I use for some small self hosting services. I never use all my RAM and I don't see any RAM spikes other than when I install/compile things which I haven't done in months. I restarted the machine a couple of times, but the SWAP will eventually go right back up to 100%.

I have an Ubuntu server/yunohost setup and found: https://askubuntu.com/questions/157793/why-is-swap-being-used-even-though-i-have-plenty-of-free-ram

My cat /proc/sys/vm/swappiness value is indeed 60. Im not sure what would reduce the SWAP space usage.

Would changing this swappiness value help? Anyone come across this issue before?

EDIT: Found out what it is, its the matrix server that is running on the system. Its taking up a significant amount of swap. Found out via:

smem -s swap -r -p

turning that off, the system is now using 90% less SWAP. /opt/yunohost/matrix-synaps was the process.

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[–] 4 points 1 year ago (1 child)

"hey, this memory page is never used and this file block is used a lot, so I'm going to put the memory page on disk and the file block in memory and everything will be faster."

except when not, like when I just copied a multi GB file, it was cached in RAM to be not read again for long, but at least half of my running programs are swapped out. Additionally if swap is o SSD, it has put totally unnecessary wear into it by doing this

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  • [–] 10 points 1 year ago (1 child)

    That's why you can adjust swappiness, or designate a different high-endurance storage device for it.

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  • [–] 2 points 1 year ago* (1 child)

    my swappiness is 0. yet my swap usage isn't. plenty of "available" memory (as in, multiple GB)

    or designate a different high-endurance storage device for it.

    good luck with that on a laptop. maybe the swapiness setting could just work sensibly

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  • [–] 1 point 1 year ago (1 child)

    “sensibly” “intuitively” and “performant” are all different objectives and I assure you kernel devs working on such a central subsystem are primarily optimizing for one.

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