d2b321ea93
Mask off disabled counters based on PERF_GLOBAL_CTRL *before* iterating over PMCs to emulate (branch) instruction required events in software. In the common case where the guest isn't utilizing the PMU, pre-checking for enabled counters turns a relatively expensive search into a few AND uops and a Jcc. Sadly, PMUs without PERF_GLOBAL_CTRL, e.g. most existing AMD CPUs, are out of luck as there is no way to check that a PMC isn't being used without checking the PMC's event selector. Cc: Konstantin Khorenko <khorenko@virtuozzo.com> Link: https://lore.kernel.org/r/20231110022857.1273836-7-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.