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I ran across following definition of vm.swappiness:

The swappiness parameter controls the tendency of the kernel to move processes out of physical memory and onto the swap disk.

So, if I have no swap partition any change on this parameter will be in vain?

I'm pretty much sure it is so, but I wanted to check. If I'm writing from another system over Ethernet to my running board with attached disk, data is first being cached (via memory mapping), and then written to disk via DMA right?

What if my RAM gets full in the meantime?

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You didn't say what OS you're using, so I'm assuming Linux. In that case, usually the OOM killer does its job trying to free some memory. You can also expect kernel crashes in such situations. To answer the 1st question, no, if you don't have any swap, the vm.swappiness sysctl won't have any effect.

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  • In that case, I guess, OOM killer will first try to free RAM by removing (discarding?) Ethernet data in buffer cache, while leaving application and kernel pages untouched? Commented Feb 29, 2016 at 12:11
  • OOM killer tries to kill the most memory-consuming application(s) in order, so I don't think Ethernet data will be (directly) affected. Hardware/OS info would help a lot, though. Commented Feb 29, 2016 at 12:15
  • Yeah, sorry, Its ARMv7 architecture, Ubuntu 13.10. Understand, but I also "feel" that I need to investigate subject further... How come that I see that kswapd process is active? Does he not relate to swap partition? Commented Feb 29, 2016 at 13:02
  • kswapd is a kernel-related process, and it's related to swap in general, it doesn't care much if you actually have a swap partition or not. When I asked for hardware info I meant configuration (memory, storage) so I can try to assess why you chose not to have a swap partition in the first place and how much memory you do have. Commented Feb 29, 2016 at 13:05
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    If you have so much storage space, why not create a swap partition and use it? Have a look at mkswap, swapon and /etc/fstab Commented Feb 29, 2016 at 16:43

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