ubuntu-phone team mailing list archive

[John Johansen <john.johansen@xxxxxxxxxxxxx>]

On 08/06/2015 04:50 PM, Chris wrote:
> 
> 
> On 06/08/15 16:35, Oliver Grawert wrote:
>> hi,
>> Am Donnerstag, den 06.08.2015, 14:33 +0100 schrieb Matthew Paul Thomas:
>>
>>> Many people do not understand this. Even worse, they think the
>>> opposite -- that closing apps will make their phone faster somehow.
>>> This is understandable if they're used to PCs, which do work the way
>>> they imagine: background apps can consume processing time, and by
>>> sitting in RAM they may cause a foreground app to use slow swap space
>>> instead. But neither is the case in Ubuntu Touch. Background apps are
>>> put to sleep, so they don't take up processing time.[1] And swap space
>>> is small, and may not even exist at all in the long run,[2] because if
>>> memory is really needed the OS can just close background apps
>>> automatically.
>> we use zram across the board for swapping currently, not actual swap
>> space ... so you wont actually notice slowdowns when something swaps (i
>> commented on that bug too btw)
>>
>> while all of the above is correct it sadly doesn't really match
>> reality ... on a 1G device like krillin the app lifecycle management (or
>> rather the in-kernel lowmemorykiller that we use) usually don't let you
>> have more than 2-3 apps active in ram and you end up with OOM killed
>> apps a lot ...
>>
>> if an app gets OOM killed it will be completely flushed from RAM, there
>> is only a screenshot in unity8 representing it ... once you flip this
>> app back into foreground in the UI it will be loaded from disk, this
>> isn't much different from swapping to disk or any other disk I/O
>> operation, so all you do is to move the slowness into another place.
>>
>> if you now take away the ram for one unkillable app on a 1G device your
>> possible app count goes down from 3 to 2 before you cause any slowness
>> by re-loading the apps, so on these devices it matters a lot if you keep
>> an unkillable app running or not just to compensate for its slow startup
>> time.
>>
>> ciao
>> 	oli
>>
>>
> Now you got me guys totally confused and interested. From now on I will be testing, say one day without switching apps off, another as I normally do - with switching.
> I don't use that many of them anyway, but indeed I did have a PC model in head - less apps = more RAM free...
> 
Still is true to a degree. Linux will use any "free" ram as cache and that
can speed up some apps. It will depend on what they do, how much of the app
needs to be resident etc.