SLES12SP4: Swapping Behavior

SUSE Product Topics SLES Configure-Administer
1

Hello,
we have some strange swapping behavor.

Using SLES12SP3 we had no major swapping with vm.swappiness = 0

After Upgrading to SLES12SP4 we had some crashes because the operation system could’nt swap. We figure out that vm.swappiness = 0 disables swapping now. So we modify the parameter to vm.swappiness = 1, to enable swapping at all.
With SLES12SP4 and vm.swappiness = 1 we observe a more progressive swapping. The servers swaps out small amounts of memory, even if there is enough memory available. Especially updating with zypper creates a swap with few KB.

Do you have informations about that behaviour?

BR
Christian

2

Hi
Did you also set the vm.vfs_cache_pressure? I run;

vm.swappiness=1
vm.vfs_cache_pressure=125

https://www.kernel.org/doc/Documentation/sysctl/vm.txt

3

Hi,
thanks for your advice.
I applied your settings on some servers.

4

Hello,
after two weeks of testing, the parameter vm.vfs_cache_pressure = 125 has no effect.
System won’t reintegrate the swap. Between the screenshot are 30 minutes.

5

Hi
So your wanting it to use it more? If so reduce the pressure number. By default it’s 60.