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SolidHal / PrawnOS

Libre Mainline Kernel and Debian for arm laptops
https://www.PrawnOS.com
GNU General Public License v2.0
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Add ZRAM kernel module #230

Open joshbowyer opened 3 years ago

joshbowyer commented 3 years ago

Module or flag. This is pretty standard on ChromeOS as well as most Linux distros now (it has been added to Mobian for Pine devices too)

SolidHal commented 3 years ago

Seems like it would give us some nice performance improvements on these low-ram systems. Could users with ChromeOS report how large of zram partitions are used on 2GB and 4GB models?

joshbowyer commented 3 years ago

I dont use ChromeOS but on Mobian (Debian for Pine) we generally set it to 50% and all cores (4), and it works very well

SolidHal commented 3 years ago

CONFIG_ZRAM was actually already enabled on the armhf kernel. Now enabled on the arm64 kernel as well. Next is to setup the userspace config to take advantage of it.

joshbowyer commented 3 years ago

It isnt on my install and I installed v1.1... to enable in userspace install zramswap and edit /etc/defaults/zramswap

SolidHal commented 3 years ago

https://github.com/SolidHal/PrawnOS/blob/f8459643606db4c4e4a489588bc7312e21e81109/kernel/resources/armhf/config#L1478 shows it is built in to the kernel. Its not a module, so it won't show up in lsmod. Actually, nothing is a module right now. on my veyron-speedy, I see /dev/zram0 which further confirms it is enabled.

By "on all cores (4)" are you saying there is a zram device per core?

joshbowyer commented 3 years ago

Yes, it utilizes all cores which is optimal, otherwise you only get 1/4 the swap capacity/processing.

Ill have to double check the exact error Im getting because when I started it it screamed about the module not existing...

SolidHal commented 3 years ago

ah, so you are talking about cat /sys/block/zram0/max_comp_streams not the number of zram devices to create? From https://www.kernel.org/doc/html/latest/admin-guide/blockdev/zram.html it looks like it automagically creates the right amount of compression streams

joshbowyer commented 3 years ago

Im not sure about how it translates to the /sys blocks, but as far as the config itself those are the variables/values we found to work best. (Im not a dev, Im a linux admin who tries to help as much as he can lol, so sorry if Im missing an obvious link here)

graves commented 3 years ago

Zram takes a parameter to set the number of devices it creates, the default is 1 which is why you only see /dev/zram0 created.

So you'd either need to build it as a module and load it with:

modprobe zram num_devices=4

or add the parameter to the kernel parameters when you build the kernel.

SolidHal commented 3 years ago

@graves thanks but my confusion is around if we want a zram device per cpu or if max_comp_streams is what we want per cpu. I'm leaning towards max_comp_streams since the documentation mentions it now automatically sets max_comp_streams based on the number of cpus