SLE (x86_64 RAM 512 M):¶

- install medium: SLE-15-SP3-Online-x86_64-Build.162.7-Media1.iso (RC1Candidate)
- RAM 512 M | 1 CPU | Hard disk 20 G
- linuxrc version: 7.0.30
    - linuxrc params: regurl=http://all-162.7.proxy.scc.suse.de YDEBUG=1
- Registering 7 modules: Basesystem, Server, Legacy, Web and Scripting, Containers, Desktop and Development
- System Role: SLES with GNOME

**Without zram:**
1. no params
 Stuck in 'Read device configuration'

**Only zram.swap**
2. zram.swap=512M
 System installed and boots OK
3. zram.swap=1G
Comparing with 512M, speeds up in the registration and installation of package aprox. 20 second (not very significative)
4. zram.swap=2G
Comparing with 1G is lightly slower.

**Only zram.root**
5. zram.root=512M
   Very SLOW, unusable when registering the first module.
6. zram.root=1G
SLOW, unusable when registering the first module.
7. zram.root=2G
   Very SLOW, unusable even before selecting modules

**Combination of zram.root and zram.swap**          
8.   zram.root=512M zram.swap=512M  
9.   zram.root=1G zram.swap=512M)
10. zram.root=512 zram.swap=1G)   
11.  zram= 1 (zram.root=1G zram.swap=1G)

In the 4 cases system installed and boots OK
In registration/installation of package phases there were no significative difference of time.
512M/512M combination was the first to finish installation by 15 seconds (other factors could affect the time but was not the last one)
so  1G/1G seems to me a good default to give some more margin.

12. AutoYaST  with no params (using some more cumbersome [profile](https://github.com/os-autoinst/os-autoinst-distri-opensuse/blob/master/data/autoyast_sle15 /autoyast_multi_btrfs.xml) and 4 disks.
    Stuck in 'Initializing' dialog.
13. AutoYaST  zram=1
    Installations succeeded and system booted properly.

TW (x86_64 RAM 512 M):¶

- install medium: openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210316-Media.iso
- RAM 512M | 1 CPU | Hard disk 20 G
- linuxrc version:  7.0.30
- linuxrc YDEBUG=1

**Without zram:**
1. no params
   linuxrc error

**Only zram.swap**
2. zram.swap=512M
3. zram.swap=1G
4. zram.swap=2G
   linuxrc error in all of them

**Only zram.root**
5. zram.root=512M
6. zram.root=1G
7. zram.root=2G  
   linuxrc error in all of them

**Combination of zram.root and zram.swap**
8. zram= 1 (zram.root=1G zram.swap=1G)
9. zram.root=2G zram.swap=2G
   linuxrc error in all of them

TW (x86_64 RAM 1024 M):¶

- install medium: openSUSE-Tumbleweed-DVD-x86_64-Snapshot20210316-Media.iso
- RAM 1024M | 1 CPU | Hard disk 20 G
- linuxrc version:  7.0.30
- linuxrc YDEBUG=1
- System Role: Desktop with KDE Plasma

**Without zram:**
1. no params
   Stuck in 'Add-On Products'

**Only zram.swap**
2. zram.swap=512M
3. zram.swap=1G
4. zram.swap=2G
No difference among them. All work.

**Only zram.root**
5. zram.root=512M
6. zram.root=1G
7. zram.root=2G 
   All got stuck after partitioning.

**Combination of zram.root and zram.swap**
8.  zram.root=512M zram.swap=512M  
9.  zram.root=1G zram.swap=512M)
10. zram.root=512 zram.swap=1G)   
11. zram= 1 (zram.root=1G zram.swap=1G)
    All worked fine in similar way, as the zram.swap seems to be the most important factor.

Comparing our current openQA configuration with and without zram=1:

select_modules_and_patterns_without_zram@aarch64 vs select_modules_and_patterns_with_zram@aarch64
select_modules_and_patterns_without_zram@64bits vs select_modules_and_patterns_with_zram@64bits
select_modules_and_patterns_without_zram@ppc64le vs select_modules_and_patterns_with_zram@ppc64le
select_modules_and_patterns_without_zram@s390x-kvm-sle12 vs select_modules_and_patterns_with_zram@s390x-kvm-sle12

Summary of improvements on time executions:

1 min in scc_registration for aarch64 and 64bits
4 mins in select_patterns and await_install in 64bits.