zRAM

[Leszek Lesner]

Am Sonntag, 9. Juni 2013, 12:14:27 schrieb Ali Linx:
> On Sun, Jun 9, 2013 at 11:08 AM, <leszek.lesner at web.de> wrote:
> > Ok a simple suggestion from me. Why don't we decidebto enable zram (with
> > zram-config) for the alpha version and see how itnworks out for the
> > testers. We can disable this afterwards if the test fails.
> > But I highly doubt that you will see any downside in using zram.
> > And btw. as I don't think it os clear to everyone zram enabled means a
> > virtual swap partition gets mounted into the system. The location of this
> > swap partition is however instead of the traditional one a virtual
> > compressed ram drive. I hope that this is understandable.
> > Please +1 if you also want zram enabled by default in the alpha images.
> 
> Hello Leszek,
> 
> Thank you for your suggestion, I like the idea but ... Before we take a
> vote, may I ask something?
> If someone with 512MB RAM and has 1GB SWAP Partition, how zRAM will do any
> help in this case?

It will raise the SWAP size. This in particular will not help much(if you 
already have 1 GB). But for SWAP files/partitions you can set priorities. So 
that for swap it should use zram first and then the hdd or ssd in your 
computer. 
And one rule that applies always RAM is faster than hdd/ssd. So swapping out 
to a compressed ramdrive might be a little bit slower than directly writing to 
your memory (this depends on the cpu and the number of cpus) but it is 
definitely faster then writing to your harddrive. 
On much workload which uses lots and lots of memory (usually the webbrowser is 
a memory hungry beast no matter if chromium or firefox or xyz) this could 
dramatically help the performance. (especially also when you think about live 
usb sticks with persistency files/partitions + swap file/partiton on it - I 
admit this might be a rare case but I have seen this before more than once 
already) 

> 
> When I first starting using Ubuntu and Lubuntu, when I first joined the
> Ubuntu Forms, the GURUs and the Expert people over there taught me
> something.
> If you have 1GB-2GB RAM or more, SWAP Partition = RAM
> If you have LESS than 1GB RAM, SWAP Partition = 2 * RAM

It depends. 
Chromium for example sometimes needs lots and lots of ram and in this case it 
might be wise to also have more SWAP space for this. 
As /tmp nowadays also tends to be written to ram it might be also helpful to 
have a bigger swap file/partition depending on how you work and what 
applications you use. 
Audacity (the audio editor) for example writes everything to /tmp if you don't 
save your project somewhere. This can fill the /tmp directory very fast if you 
are cutting an interview or a large music file. 

> 
> Whenever I use my test machines with 512MB RAM, I always set SWAP Partition
> to be 1GB RAM. NO MATTER how much my HDD Size is.
> Having that said, I do have NO problems at all whether installing from a
> LiveCD or LiveUSB.

Not everyone who wants to install Lubuntu has a swap space on disk for it on 
first installs. It might be very convenient then to double the memory available 
just by enabling zram (which uses the same amount as RAM is available as 
virtual swap space compressed in RAM). At least it is more convenient than 
telling those people to firstly create a swap partition with gparted and either 
enable it with the terminal or reboot the live system to be able to install 
the system on the pc. 

I hope that explains some things .
Ah and btw. we here at ZevenOS also tested zram in Neptune (yeah I am the main 
dev of Neptune & ZevenOS) for about half a year and it worked fine so far and 
we made particullary good experiences with live systems + persistency (which 
is one of Neptunes primary goals).