Linus Torvalds announced Linux 5.9-rc3 L (release candidate 3), which he has described as being a fairly calm release cycle overall. Among the many new features and drivers for hardware merged this time around are security and scheduler fixes. Intel platforms have gained support for FSGSBASE while Arm platforms now use the newer ‘schedutil’ CPU frequency governor.
The inclusion of FSGSBASE support means that context switch (the time taken to switch from running one process - tasks in kernel speak - to another) latency will decrease. Since Linux uses context switches to enable it to run many tasks on a single CPU, as well as every time a program makes a ‘system call’ into the kernel for some service it needs, reducing this time is a net win.
Meanwhile, Intel platforms have also gained support for the new SERIALIZE instructions that will be used to mitigate potential future security exploits. On the Arm front, switching to ‘schedutil’ (already the default on x86) will improve the ability for the kernel to assist the underlying hardware platform in making CPU frequency changes appropriate to the actually running workload. This should mean future Arm-based phones and even servers stand to benefit.