lubuntu-qa team mailing list archive

[Jörn Schönyan <joern.schoenyan@xxxxxx>]

Am 26.10.2013 20:37, schrieb Leszek Lesner:
> == The new modern situation (with 13.10¹): ==
> * RAM + ZRAM
>
> The RAM is backed up by a SWAP partition which is stored on a virtual
> compressed ram device. Under Lubuntu
> 13.10 this device can use half of the physically available memory.
> Writing and reading to and from RAM is a hell lot faster than to disk
> (even to an SSD). This means there is no bootlneck
> when the system swaps out to ZRAM with its default swappiness settings.
> Setting the swappiness lower here would make a change but
> a very minor only (noticable only via benchmarks). And lowering it here
> might lead to a faster reaching of the second
> bottleneck. So avoiding swapping and letting the RAM be filled and
> swapping late especially when RAM is very full will slow down the
> system and produces noticable lags. Those lags might be even harder in
> this case because the pages need to be compressed into RAM and
> when new pages need to be placed into RAM at the same time this might
> lead to a long cpu 100% compressing decompressing moving loop.
> Letting the swappiness at default (60) or even set it higher to 100
> would help avoid this bottleneck as swapping early would avoid
> RAM running full too fast.
I can completely conform this. I did an experiment, because I have to
set up an old notebook in the next days, which only has 256 Megs of RAM
and is a working machine. Of course, the background is the EOL of WinXP.
There needs to be running a software called "ElsterFormular" which is
needed for the tax office in germany if you are self-employed. Funny
thing: you need Wine to run it - but there exists a linux version which
nobody can download because they say it is too expensive for them! But
that's another story.

ElsterFormular is quite big right now, so ZRAM is a lot of help. I set
up a VM and tried if everything would work. I just saw that it worked
and _then_ I tried to reduce the swappiness - I think I set it to 15 or
20, but I'm not 100% sure which of this it was. I didn't measure the
time, but at least it was twice as much time, likely more.
>
> So all in all when you see this scenarios I have to say that the default
> value of swappiness 60 makes the most sense as the default value
> of lubuntu. Changing it for the next release is something I would not
> recommend.
>
All in all, I second that.

Jörn