zram swap support for the PBP; aka: "how to download more RAM"

[Arglebargle]

Hey all,

Last month I posted a simple zram-swap script that I wrote for my PBP on IRC for people to use. I took some time to package it and make it "release worthy" and pushed it to github with updates today: https://github.com/foundObjects/zram-swap

This makes a huge difference if you're memory constrained on your PBP, and even if you aren't I encourage you to check it out simply to avoid the NAND wear of swapping to your eMMC when you eventually do need to swap.

I also added a fixed-size swap feature for people who know ahead of time exactly how much swap they want, so if you're doing something like building GCC with -lto on the PBP and need 10+G swap I've got you covered: just set "_zram_fixed_size=10G" in the /etc/default/zram-swap config file along with your prefered swap algorithm and you're good to go. Yes, you can use lzo-rle.

README.md:

Code:

# zram-swap Simple zram swap setup + teardown script for modern systemd Linux systems https://github.com/foundObjects/zram-swap ### Why? There are dozens of zram swap scripts out there, but most of them are overly complicated and do things that haven't been neccessary since linux 3.X or have massive logic errors in their swap size calculations. This script is simple and reliable, modern and easy to configure. ### Installation ``` git clone https://github.com/foundObjects/zram-swap.git cd zram-swap && sudo ./install.sh ``` ### Usage zram-swap.service will be started automatically after installation and during each subsequent boot. The default allocation creates a zram device that should use around half of physical memory when completely full. The default configuration using lz4 should work well for most people. lzo may provide slightly better RAM utilization at a cost of slightly more expensive decompression. zstd should provide better compression than lz* and still be moderately fast on most machines. On very modern kernels the best overall choice is probably lzo-rle. Edit `/etc/default/zram-swap` if you'd like to change compression algorithms or swap allocation and then restart zram-swap with `systemctl restart zram-swap.service`. Run `zramctl` during use to monitor swap compression and real memory usage. ### Debugging Start zram-swap.sh with `zram-swap.sh -x (start|stop)` to view the debug trace and determine what's going wrong. To dump the full execution trace during service start/stop edit `/etc/systemd/systemd/zram-swap.service` and add -x to the following two lines: ``` ExecStart=/usr/local/sbin/zram-swap.sh -x init ExecStop=/usr/local/sbin/zram-swap.sh -x  end ``` ### Compatibility This should run on pretty much any recent (4.0+? kernel) Linux system using systemd. If anyone wants to try it on something really old and let me know how far back compatibility goes I'm interested, but I don't have any legacy systems to test on at the moment. The script will also work on non-systemd Linux without issue and I welcome PRs supporting SysVinit.