Swap Space Not Being used LVM+LUKS

hadadat · n00b Joined: 16 May 2015 Posts: 16

I recently changed my partitioning to use LVM + LUKS since I made that change my swap space isn't being used even though it's reported as active

I have some programs that I need to run that consume a bunch of memory. Previously it would just activate my swap and the process would finish. Now the process consumes all memory and my swap space is not being used.

I checked dmesg, but there doesn't seem to be any messages about swap or memory usage in there.

Here's some info

Hu · Moderator Joined: 06 Mar 2007 Posts: 21618

Is the device is listed in /proc/swaps? It should be, based on the deprecated output you provided. What is the output of free -m? Why do you think that the swap device is not usable? The system may elect not to swap in some cases. Are you seeing failures that you believe would not occur if swap was enabled?

hadadat · n00b Joined: 16 May 2015 Posts: 16

russK · l33t Joined: 27 Jun 2006 Posts: 665

hadadat,

Did you mkswap ? Maybe redo it regardless:

hadadat · n00b Joined: 16 May 2015 Posts: 16

Hu · Moderator Joined: 06 Mar 2007 Posts: 21618

I use encrypted swap on machines I plan to hibernate. I have done this for years and have never noticed performance problems at the scale you describe, neither on laptops nor on desktops.

russK · l33t Joined: 27 Jun 2006 Posts: 665

hadadat,

If you're still having the issue maybe try running some common benchmarks and make sure the machine is otherwise performing as it should. Sometimes a machine can have issues that go unnoticed until you hit something like this.

Regards

P151 · n00b Joined: 25 Sep 2016 Posts: 6

1clue · Advocate Joined: 05 Feb 2006 Posts: 2569

@hadadat,

Does this tool which consumes all memory require 8g or does it automatically consume all available memory no matter what size your memory is?

The others posting have covered everything I can think of regarding the mechanics of swap, but I have other comments regarding your use case.

In my strongly held opinion, to actually swap memory to disk due to lack of memory is always an error condition. Speaking directly to hardware use, swap is nearly catastrophic in what it does to your system. It causes the system to slow down to a relative crawl and it causes unnecessary disk wear. To have a system which continually uses swap in its normal day-to-day business is asking for trouble.

The system I'm using has actually used swap exactly twice. The first time I upgraded from 6gb RAM to 12gb RAM, and the second time I doubled it again. I'm now using 24gb RAM, still have swap configured but have not "used" it for a long time. The box is about 5 years old. I use "swap" not only for traditional swap but also for tmpfs.

Getting back to your use case, if the app you're using requires 8g RAM and cannot be configured to use less, then I recommend buying more memory. If it automatically grabs everything the system has and cannot be configured to not do that, then it's my strongly held opinion that you have crappy software and should look for an alternative.