[CentOS] Why swap if there's still physical memory available
Les Mikesell
lesmikesell at gmail.com
Mon Nov 16 23:02:01 UTC 2009
nate wrote:
> 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
>
Also, the top values may not tell the whole story - RES should include
paged-in code plus memory allocated by the program. VIRT includes code
not paged in yet and linked shared libraries, so the difference may not
all be in swap.
--
Les Mikesell
lesmikesell at gmail.com
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