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The way to store the LBR information from a PEBS LBR record can be reused in Architecture LBR, because - The LBR information is stored like a stack. Entry 0 is always the youngest branch. - The layout of the LBR INFO MSR is similar. The LBR information may be retrieved from either the LBR registers (non-PEBS event) or a buffer (PEBS event). Extend rdlbr_*() to support both methods. Explicitly check the invalid entry (0s), which can avoid unnecessary MSR access if using a non-PEBS event. For a PEBS event, the check should slightly improve the performance as well. The invalid entries are cut. The intel_pmu_lbr_filter() doesn't need to check and filter them out. Cannot share the function with current model-specific LBR read, because the direction of the LBR growth is opposite. Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/1593780569-62993-14-git-send-email-kan.liang@linux.intel.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.