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On platforms supporting Intel Turbo Boost Max Technology 3.0, the maximum turbo frequencies (turbo ratio) of some cores in a CPU package may be higher than the other cores in the same package. In that case, better performance can be achieved by making the scheduler prefer to run tasks on the CPUs with higher max turbo frequencies. On Intel® Broadwell Xeon systems, it is optional to turn on HWP (Hardware P-States). When HWP is not turned on, the BIOS doesn't present required CPPC (Collaborative Processor Performance Control) tables. This table is used to get the per CPU core maximum performance ratio and inform scheduler (in cpufreq/intel_pstate driver). On such systems the maximum performance ratio can be read via over clocking (OC) mailbox interface for each CPU. This interface is not architectural and can change for every model of processors. This driver reads maximum performance ratio of each CPU and set up the scheduler priority metrics. In this way scheduler can prefer CPU with higher performance to schedule tasks. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.