Re: Btrfs by default, the compression option
Kamil Paral wrote on Wed, Jul 08, 2020:
On Wed, Jul 8, 2020 at 8:26 AM Chris Murphy
<lists(a)colorremedies.com> wrote:
> D. Which directories? Some may be outside of the installer's scope.
>
> /usr
> /var/lib/flatpak
> ~/.local/share/flatpak
I have a concern regarding games. Currently, we have a few a bit more
demanding titles on Flathub already, like 0AD, Xonotic or Albion Online. In
the glorious future (tm) we might get more. Games are very sensitive to
available CPU cycles and context switching and usually come with their data
files already compressed. Including the btrfs compression by default on
flatpak dirs could lead to lowered performance whenever the game tries to
load some assets (older titles do that during the loading screen, newer
titles stream new assets constantly during gameplay and any slowdown
manifests as game stuttering).
Please test, but if a file is deemed not compressible (based on, not
sure what? the first few blocks?) then it will be stored in the
non-compressed version.
You can check with compsize after the fact if the file had been
compressed or not.
This should be true unless the compress-force mount option is used, even
the chattr is only a hint
I'm personally more concerned about reduced performance in e.g.
my web
browser than disk wear out. I don't see much harm in compressing /usr,
because it's a read-only location that gets loaded once when the app starts
(it might delay the app startup a bit, though, and decrease the perceived
snappiness of the desktop). But I'm concerned about compressing locations
which are hit often, like ~/.var or ~/.cache. I've had my 120GB SSD for 5
years and I'm just at 10% of expected TBW (total bytes written). If the SSD
lasts 50 or 100 years is not really important for me, but the desktop and
app responsiveness is (and game performance, of course:)). I think write
amplification is a problem specific to devices with SD cards, and for
anyone else, it might be better to leave it unset and let people enable it
(it's simple) if they want it for their use case.
This obviously needs testing on a wide variety of hardware but I haven't
noticed any difference in the feeling on an intel laptop (kabylake i5
throttled at 2GHz) ; that being said firefox isn't the most responsive
app in my book...
--
Dominique