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From: Arno Welzel <usenet@arnowelzel.de>
Newsgroups: comp.mobile.android
Subject: Re: What is your experience with Samsung "RAM Plus" virtual memory
 expansion?
Date: Mon, 9 Dec 2024 00:46:19 +0100
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Frank Slootweg, 2024-12-07 14:14:

> Arno Welzel <usenet@arnowelzel.de> wrote:
>> Frank Slootweg, 2024-12-06 12:51:
>>
>>> Andy Burns <usenet@andyburns.uk> wrote:
>>>> Edward.C wrote:
>>>>
>>>>> I think it depends on your usage. If you always have many apps running 
>>>>> at the same time, maybe it can give slight improvement in performance.
>>>>>
>>>>> I have disabled it and never noticed any difference, probably because I 
>>>>> have 12GB of RAM on my A55.
>>>>
>>>> Given the way Android apps save their state and are then ready to be 
>>>> killed when there is pressure on memory, ready to be reloaded "as they 
>>>> were", then using swap seems a bit pointless?
>>>
>>>   Yes, but not all apps can be killed and reloaded/restarted "as they
>>> were". For example those which depend on external data or/and state. For
>>> those apps, you want them to be swapped instead of killed.
>>
>> By definition an app *must* support the fact, that it can be killed at
>> any time. Even rotating the display will kill and restart the current
>> running activity. That's the reason, why dialog boxes should not be used
>> but UI fragments instead since the state of fragments will be handled by
>> the OS instead of the app.
>>
>> But on the other hand it depends on the app developers how good the
>> implement state changes.
> 
>   My/the point is that not all apps *can* be designed that way. It might
> be that *if* they can be designed that way, they *must* be designed that
> way. But an app developer can not be required to do the impossible.

Android *will* kill app activities all the time. An app which can not
deal with that, is mostly useless since - as I explained - even rotating
the display will cause this. Yes, some apps just cope with that by
disabling display rotation as long as the main activity is in the
foreground.

Also see here:

<https://developer.android.com/reference/android/app/Activity#onCreate(android.os.Bundle)>

<https://developer.android.com/reference/android/app/Activity#onSaveInstanceState(android.os.Bundle)>

<https://developer.android.com/reference/android/app/Activity#onRestoreInstanceState(android.os.Bundle)>

[...]
>   Also note I mentioned in the part you snipped, if all apps/programs
> could be designed that way, we wouldn't have paging/swapping on real
> computers, but we do. Guess why that is?

On "real computers" an application process will not be killed just
because you minimize a window. And paging also has nothing to do with
that either but is just the process to move RAM pages to a swap file if
not needed - regardless if there is a process running or not.

-- 
Arno Welzel
https://arnowelzel.de