[CentOS] Why swap if there's still physical memory available

nate centos at linuxpowered.net
Mon Nov 16 22:41:18 UTC 2009


yanagik317 wrote:

> I guess the answer may not be that simple and I most likely haven't
> described everything that could have influenced the kernel's
> decision-making, but how does Linux decide how much of a process to be
> swapped out?  I guess I could read the documentations on the Linux
> kernel, but does anyone have more general answers ready to be dispensed?

Linux by default will try to swap less accessed regions of memory
when memory pressure starts to get tight(say less than 25% of memory
is free), if you want to override this behavior look to the
'swappiness' setting

> I haven't done anything with sysctl, if that comes into play at all.

It can if you want

vm.swappiness = 0

To tell the kernel not to swap unless it *really* needs to

nate




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