How To Set And Use ZRAM swap

[enmus]

@qubist

@enmus

after clean install someday.

1. Are there any advantages in doing all that after a clean install?
2. Which are the additional steps (if any) during/after a clean install which you consider useful in regards to doing all that?

1. No. it’s just that for me - reminder what and how to do it after the Qubes OS clean install I plan.
2. No additional steps. My newest finding is that it’s not necessary to provide dom0 with more than 2GB zram.

@qubist

IOW how would you approach a clean install?

It’s offtopic, but if you asked

Clean Reinstall + Install Packages and Previous Configs as a Way of Backup/Restore Process

@enmus I’ve attempted to rewrite the title to be more explicit about the issue. But let me know if I totally butchered it and just change it back. Let me say that I totally understand your reasoning for this. Actually, I did exactly what you suggested in your first post. When moving to 4.1 I didn’t restore the default templates. Instead, I opted to reinstall all the software I had there. To do this I used commands like dnf history (on fedora templates) to see what else I had installed. There s…

@qubist

What are the possible disadvantages? (besides the obvious extra CPU load related to de/compression)

3. Beside CPU, none that I’m aware of, especially if swap as a backup device is set to avoid system crash once the (z)RAM is exhausted. The fact that zram is included both in Fedora and Debian now should say enough.

@qubist

What about using zswap for that? Couldn’t the compression of swapping (less bytes written) reduce the write cycles and wear of SSD?

As I said above, I don’t want zswap to compete with and intercept zram and write to swap. I want to avoid zswap acting as a swap cache in front of it. If they are both enabled also leads to wrong zramctl statistics because obviously zram is then mostly unused; this is because zswap intercepts and compresses memory pages being swapped out before they can reach zram. Swap is there allowed in very rare cases, and I can accept wearing my SSD in those rare cases. Not to say that I can format zram and use it temporary as any other block device, but much faster, right? Also, zswap decompressing to swap makes me extremely uncomfortable since under specific circumstances it can be very dangerous.

It’s all there in those links I posted

@qubist

Can you suggest a way to benchmark and compare a system in each combination:

I haven’t thought about this, but I’d probably use sysbench and vmstat. And systemd-analyze?
This could give you an idea, too.

@qubist

How about Windows templates and their derivative qubes? Will Xen zram/zswap them implicitly? Or is anything additional necessary? (Suppose swapping/paging is explicitly disabled in a Windows VM)

I’m not sure I understand this. Beside disabling paging in Win qubes in order to spare SSD, I see creating RamDisk meaningful only to put browser cache there for example.