Linux 5.4 To Allow Adjusting Intel TCC Thermal Activation Offset For Better Performance
In addition to adding Intel Icelake support to the kernel's processor thermal / int340x code, there is an interesting change with the thermal management updates for Linux 5.4 to potentially boost the performance on Intel platforms.
The change to the Intel's int340x processor thermal device code allows for reading and adjusting the TCC offset. The TCC activation offset allows for setting the thermal offset in relation to the TjMAX value for when the thermal throttle activation behavior is triggered.
Intel open-source developer Srinivas Pandruvada confirmed in the patch that the TCC (MSR_IA32_TEMPERATURE_TARGET) tweaking can indeed help with performance, "This change will be useful for improving performance from user space for some platforms, if the current offset is not optimal."
If the default TCC value for a given platform is too conservative, with Linux 5.4+ it's then possible to raise that threshold (or lower the offset in relation to TjMAX) or likewise if wanting to enforce a cooler-operating system that TCC offset can be increased. Under some systems the TCC offset is also adjustable via the BIOS/firmware.
That's what I find most interesting with the thermal management updates for Linux 5.4 along with the Icelake IDs added, but besides that it's mostly fixes.