On a sunny day (Sat, 25 Jan 2020 09:00:04 +0000) it happened Richard
Kettlewell  wrote in
:

>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.

If the swap file is full then what will happen?


>> Also the same stuff running on a normal PC did not cause lots of
>> unrelated things to get swapped.
>> One of the links I gave shows there was a recent modification in the
>> way the kernel
>> handles caching.
>> From:
>> 
https://unix.stackexchange.com/questions/253816/restrict-size-of-buffer-cache-i
n-linux
>> all the way at the bottom of the page:
>> "Since Linux 2.6, [the bdflush] system call is deprecated and does
>> nothing. It is likely to disappear altogether in a future kernel
>> release. Nowadays, the task performed by bdflush() is handled by the
>> kernel pdflush thread." man7.org/linux/man-pages/man2/bdflush.2.html
>> \u2013 sourcejedi Feb 22 '19 at 1:05
>
>2.6 is not ‘recent’, it was released in 2003.

OK,
There was more I found online however on that subject, changes in 4.?

Anyways, now it _decreases_ swap:
Fri 24 Jan 2020 03:10:42 PM CET:
MiB Mem :   3906.0 total,   2891.6 free,    378.2 used,    636.2 buff/cache
MiB Swap:    100.0 total,     20.4 free,     79.6 used.   3378.8 avail Mem

Sat 25 Jan 2020 06:46:05 AM CET
Sat Jan 25 06:44:19 CET 2020
MiB Mem :   3906.0 total,   2653.7 free,    372.0 used,    880.4 buff/cache
MiB Swap:    100.0 total,     24.7 free,     75.3 used.   3380.4 avail Mem

Sun 26 Jan 2020 07:32:08 AM CET
MiB Mem :   3906.0 total,   3265.9 free,    370.6 used,    269.5 buff/cache
MiB Swap:    100.0 total,     26.9 free,     73.1 used.   3383.9 avail Mem

Seems a lot safer to me.

I was also wondering if a full swap space could explain mysterious crashes some
people had
with their SDcards?


Here is an other old model raspi with far less memory and older kernel running
24/7:

root@raspi73:~# uptime
07:50:10 up 14 days, 17:48, 11 users,  load average: 2.88, 3.00, 3.10

loaded to the maximum,
top:
KiB Mem:    448776 total,   426296 used,    22480 free,   150392 buffers
KiB Swap:   102396 total,        0 used,   102396 free,    61336 cached

root@raspi73:~# uname -a
Linux raspi73 3.6.11+ #371 PREEMPT Thu Feb 7 16:31:35 GMT 2013 armv6l GNU/Linux

No swapping whatsoever.

?

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