udev: Tune ZRAM rules for better performance

[ventureoo]

Since we ship zram by default via zram-generator, I think we should do some extra tuning through new zramtune service.

This service performs:

• Set the vm.swappiness value to 150. We need to push anonymous pages out more, once they are located in ZRAM.
• Setting idle pages re-compression (we used to have this in an udev rule, but it didn't seem to work properly).
• Set vm.watermark_scaling_factor parameter as recommended here:
  https://www.reddit.com/r/linux_gaming/comments/vla9gd/comment/ie1cnrh/

The list of changes is not too long, but it creates a convenient opportunity to define ZRAM-specific settings later on.

[ventureoo]

v2: I decided that the way of applying parameter values via a service for systemd is not good enough (the dependency on zram-generator services probably doesn't work the way as I expected), so I just modified the existing udev rules.

[Boria138]

Since we ship zram by default via zram-generator, I think we should do some extra tuning through new zramtune service.

This service performs:

* Set the `vm.swappiness` value to 150. We need to push anonymous pages out more, once they are located in ZRAM.

* Setting idle pages re-compression (we used to have this in an udev rule, but it didn't seem to work properly).

* Set `vm.watermark_scaling_factor` parameter as recommended here:
  https://www.reddit.com/r/linux_gaming/comments/vla9gd/comment/ie1cnrh/

The list of changes is not too long, but it creates a convenient opportunity to define ZRAM-specific settings later on.

If I don't confuse anything, watermarks can be turned off in vain, as here

zen-kernel/zen-kernel@4042133

[ventureoo]

Since we ship zram by default via zram-generator, I think we should do some extra tuning through new zramtune service.
This service performs:

* Set the `vm.swappiness` value to 150. We need to push anonymous pages out more, once they are located in ZRAM.

* Setting idle pages re-compression (we used to have this in an udev rule, but it didn't seem to work properly).

* Set `vm.watermark_scaling_factor` parameter as recommended here:
  https://www.reddit.com/r/linux_gaming/comments/vla9gd/comment/ie1cnrh/

The list of changes is not too long, but it creates a convenient opportunity to define ZRAM-specific settings later on.

If I don't confuse anything, watermarks can be turned off in vain, as here

zen-kernel/zen-kernel@4042133

We don't ship the latest patches from Zen in our kernel. This patch also does the same thing as setting sycstl vm.watermark_boost_factor=0, which is already included in 21f5ee4. Maybe we should disable this also for non-ZRAM users, but I'll want to leave it that way for now.

[Boria138]

Since we ship zram by default via zram-generator, I think we should do some extra tuning through new zramtune service.
This service performs:

* Set the `vm.swappiness` value to 150. We need to push anonymous pages out more, once they are located in ZRAM.

* Setting idle pages re-compression (we used to have this in an udev rule, but it didn't seem to work properly).

* Set `vm.watermark_scaling_factor` parameter as recommended here:
  https://www.reddit.com/r/linux_gaming/comments/vla9gd/comment/ie1cnrh/

The list of changes is not too long, but it creates a convenient opportunity to define ZRAM-specific settings later on.

If I don't confuse anything, watermarks can be turned off in vain, as here

zen-kernel/zen-kernel@4042133

We don't ship the latest patches from Zen in our kernel. This patch also does the same thing as setting sycstl vm.watermark_boost_factor=0, which is already included in 21f5ee4. Maybe we should disable this also for non-ZRAM users, but I'll want to leave it that way for now.

I attached the Linux zen commit so that you could read the note to it because if I understood it correctly (which may be wrong but still) the vm.watermark_boost_factor=0 parameter completely disables watermarks so there is no point in vm.watermark_scale_factor, again I may be mistaken

[ventureoo]

Since we ship zram by default via zram-generator, I think we should do some extra tuning through new zramtune service.
This service performs:

* Set the `vm.swappiness` value to 150. We need to push anonymous pages out more, once they are located in ZRAM.

* Setting idle pages re-compression (we used to have this in an udev rule, but it didn't seem to work properly).

* Set `vm.watermark_scaling_factor` parameter as recommended here:
  https://www.reddit.com/r/linux_gaming/comments/vla9gd/comment/ie1cnrh/

The list of changes is not too long, but it creates a convenient opportunity to define ZRAM-specific settings later on.

If I don't confuse anything, watermarks can be turned off in vain, as here
zen-kernel/zen-kernel@4042133

We don't ship the latest patches from Zen in our kernel. This patch also does the same thing as setting sycstl vm.watermark_boost_factor=0, which is already included in 21f5ee4. Maybe we should disable this also for non-ZRAM users, but I'll want to leave it that way for now.

I attached the Linux zen commit so that you could read the note to it because if I understood it correctly (which may be wrong but still) the vm.watermark_boost_factor=0 parameter completely disables watermarks so there is no point in vm.watermark_scale_factor, again I may be mistaken

This parameter only disables watermark boosting, not watermarks in general. As said in kernel documentation:

A boost factor of 0 will disable the feature.

https://www.kernel.org/doc/html/latest/admin-guide/sysctl/vm.html