Faster algorithm for extracting helps speed up the startup.
Anyone who installs Ubuntu 19.10 next month will find more than just a new light theme, since the download time will be faster.
Canonical engineers have tested many different options for compression installation image of Ubuntu, trying to find a compromise between the best compression, that is a relatively small file size and speed of decompression.
In our tests the most visible results have demonstrated the LZ4 decompression algorithm.
Thus, decompression of LZ4 is the default for kernels x86, ppc64el, s390 and initramfs in the respective images of the Ubuntu installer 19.10, i.e., the images that most people will install using the Ubuntu 19.10.
What is initramfs?
Initramfs is a temporary root file system loaded into memory as part of the Linux boot process. After unpacking it provides the modules needed to mount the real root file system (i.e. your hard drive).
Colin king from Canonical shares more details in his blog, explaining that: “Even at slow rotation of the carrier and slow processor longer boot time kernel LZ4 is overcome at a much faster unpacking”.
“As media becomes faster, the difference in startup time between GZIP, LZ4, and LZO is reduced, and the decompression time becomes the dominant factor of speed, LZ4 is a clear winner”.
Here it is possible to examine in more detail the test results.