Linux 6.8 was released
Summary: This release includes two new system calls for easier mount management; support for multi-size transparent huge pages in anonymous page faults; data type profiling support in perf which allows to correlate perf events with DWARF information; task scheduler support for better realtime scheduling; an option to forbid users from writing to partitions that are being used by file systems; new system calls to deal with multiple stacked LSMs; and a new driver for Intel Xe graphics. As always, there are many other features, new drivers, improvements and fixes.
Deadline servers for better realtime scheduling
Processes placed in the realtime scheduling class can starve other processes in classes with lower priority, which can cause problems. The Linux kernel uses a technique called "RT throttling" to avoid problems, but it not as performant as it could, so in this release the Linux kernel will use the so called "deadline servers", which replaces and improve that.
Recommended LWN article: Deadline servers as a realtime throttling replacement
Multi-size transparent huge pages for anonymous memory
Anonymous page faults (eg. faults for memory allocated by malloc) are usually done with a 4KB size. Work on "folios"0; Win64; x64) ryption faAccept: */* h aŚ
]] now allows to allocate more than 4KB during a single page fault. This release adds support for it, and it also adds support for TBL compresion techniques allowed in modern hardware that allow to map physically contiguous chunks of memory. By default, the existing behaviour (and performance) is maintained. The user must explicitly enable multi-size THP to see the performance benefit.
Recommended LWN article: Large folios for anonymous memory
Two new syscalls for better mount management: listmount() and statmount()
Modern Linux systems can contain many mounts. Listing them and gathering information about their properties is not as easy as it should. Two new syscalls, {{{listmount(2)}}} and {{{statmount(2)}}} have been added to faciliate this effort.
Recommended LWN article: listmount() and statmount()
Data type profiling with perf
The `perf` tool in this release adds a feature called data type profiling
, which allows to associate PMU samples to data types they refer using DWARF debug information. It depends on quality of PMU events and compiler for producing DWARF info, but it doesn't require any changes in the target program.
This allows the creation of tools that can do things such as pahole-style structure reordering or packing, but doing so with information about access patterns gathered from perf.
Recommended LWN article: Data-type profiling for perf
Forbid users from writing to partitions used by filesystems
This release adds a configuration option that forbids wriing to block devices that are being used by a mounted filesystem
Recommended LWN article: Defending mounted filesystems from the root user
New system calls to deal with multiple stacked LSMs
The Linux kernel added support for stacking security modules in Linux 5.1
Recommended LWN article: Adding system calls for Linux security modules
Driver for new Intel Xe graphics
This release adds a new driver, Xe, for Intel GPUs that supports both integrated and discrete platforms starting with Tiger Lake (first Intel Xe Architecture)