ubuntu-phone team mailing list archive

[Oliver Grawert <ogra@xxxxxxxxxx>]

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