On 25/01/2020 09:00, Richard Kettlewell wrote:
> Jan Panteltje  writes:
>> On a sunny day (Fri, 24 Jan 2020 14:54:44 +0000) it happened Richard
>> Kettlewell  wrote in
>> :
>>> Jan Panteltje  writes:
>>>> Yes, cool,
>>>> On my system it is set to 60, but WHY THEN is it filling almost the
>>>> whole memory
>>>> with cache?
>>>
>>> Because otherwise the memory would be wasted. You paid for the silicon,
>>> you’re paying for the electricity that powers it, using it store idle
>>> pages is not a good use of those resources. You are attacking a
>>> non-problem.
>>
>> I disagree, I did see the swap space increasing day after day and that
>> set of an alarm with me (normally I do a quick view on 'xosview').
>
> It doesn’t matter.
>
> What would matter is the system swqpping lots of things back in; that
> would impact performance. But you’ve not measured that, as far as I can
> tell. Nothing you’ve yet posted is inconsistent with the normal eviction
> of idle pages from RAM.
>

Is writing a page to swap the same as evicting it from RAM? Naively I
would have thought it would just mark the page as ready for eviction,
i.e. eviction from RAM would only occur after some further kind of
ageing process and/or more memory pressure.

Apologies if my terminology isn't quite correct, I did used to know the
basics of virtual memory for VMS but that was some decades ago. I don't
think I've ever read a good description of how linux (or unix) handles
it. Can anyone recommend a good technical overview of the subject, if
such a thing exists.

FWIW I would worry about a slowly growing swap file as being symptomatic
of a memory leak, but that may be due to my lack of understanding.

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