January 26, Linus Torvalds announced the release of Linux Kernel 5.5.
Linux Kernel 5.5 is the latest version, following v5.4 released at the end of November 2019. This is the first stable release in 2020, after releasing the seventh release candidate.
The file system Btrfs is implemented with two new block group profiles. This enables RAID1 with three or four copies, besides two. Also, it is added with support for new checksums, and cryptographic hashes sha256 and blake 2b. With the improved parallel processing function, it can speed up by up to 80.
Now CIFS can be used as root file system. Also, as it now supports multichannel, client can share the same SMB session over multiple TCP connections.
As BPF is improved, now it allows type checking for assembly code, and conducts safe and speedy BPF tracking. It introduces “BPF trampoline,” which allows kernel code to call into BPF programs without overhead.
As to “io_uring,” an interface for asynchronous I/O, introduced in v5.1, networked support has been enhanced. Now the processes can control the CQ ring size, and that prevents events from dropping during overflow.
KUnit, a lightweight unit testing framework, is incorporated. Using the User-Mode Linux architecture, it can run without a virtual machine or special hardware.
To improve the performance of WiFi connection, it now allows setting a queue limit based on the airtime. This was achieved by making CoDel queuing work effectively with wireless drivers.
It supports Raspberry Pi 4. There are improvements added to support the latest GPUs, like AMD Arcturus Vega-based GPU and Intel Gen12 “Tiger lake.”