Using zRAM On Ubuntu 13.04 Linux

The Linux kernel zRAM module allows for creating RAM-based compressed block devices and for common situations can reduce or eliminate paging on disk. The zRAM feature can be particularly beneficial for systems with limited amounts of system memory. It's quite easy to setup zRAM on Ubuntu Linux, so in this article are some before and after benchmarks.

For some cursory benchmarks this weekend, from an old Apple Mac Mini with 1GB of system memory and Intel Core 2 Duo T5600 processor and i945 graphics, benchmarks were conducted atop Ubuntu 13.04 with the Linux 3.8 kernel. A variety of system benchmarks were carried out immediately after a clean Ubuntu 13.04 "Raring Ringtail" development installation and then again after setting up zRAM.

On recent Ubuntu Linux releases, installing and setting up zRAM is as easy as running sudo apt-get install zram-config, with zRAM being part of the mainline Linux kernel tree. Ubuntu's zram-config package simply consists of an Upstart job for enabling zRAM at boot. You can see if zRAM is active on your system by checking the output of dmesg | grep zram.

Canonical has been looking at making greater use of zRAM on Ubuntu for low-end hardware, particularly mobile devices. Another notable current user of zRAM is Google where they have enabled this kernel feature inside Chrome OS.

From the old Apple Mac Mini with just 1GB of system memory and Intel Core 2 Duo processor, a variety of Linux benchmarks were done on Ubuntu 13.04. All of these benchmark results in full can be found on OpenBenchmarking.org within 1304219-UT-ZRAMUBUNT91. Within that result file are all of the system logs and detailed hardware/software information.
For some normal computational workloads on systems with 1GB of memory, zRAM doesn't make much of a difference unless a lot of paging is taking place.
In some odd cases though, it looks like using zRAM might actually cause a performance drop.
For normal Linux workloads these results weren't incredibly interesting or worthwhile on the Apple Mac Mini with 1GB of RAM, but those interested can go through the rest of the data. Aside from the quantitative results, the overall responsiveness of the system did seem to be a bit better when dealing with the Unity desktop and Mozilla Firefox on this memory-constrained system.