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An IA32_LBR_CTL is introduced for Architecture LBR to enable and config LBR registers to replace the previous LBR_SELECT. All the related members in struct cpu_hw_events and struct x86_pmu have to be renamed. Some new macros are added to reflect the layout of LBR_CTL. The mapping from PERF_SAMPLE_BRANCH_* to the corresponding bits in LBR_CTL MSR is saved in lbr_ctl_map now, which is not a const value. The value relies on the CPUID enumeration. For the previous model-specific LBR, most of the bits in LBR_SELECT operate in the suppressed mode. For the bits in LBR_CTL, the polarity is inverted. For the previous model-specific LBR format 5 (LBR_FORMAT_INFO), if the NO_CYCLES and NO_FLAGS type are set, the flag LBR_NO_INFO will be set to avoid the unnecessary LBR_INFO MSR read. Although Architecture LBR also has a dedicated LBR_INFO MSR, perf doesn't need to check and set the flag LBR_NO_INFO. For Architecture LBR, XSAVES instruction will be used as the default way to read the LBR MSRs all together. The overhead which the flag tries to avoid doesn't exist anymore. Dropping the flag can save the extra check for the flag in the lbr_read() later, and make the code cleaner. 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/1593780569-62993-10-git-send-email-kan.liang@linux.intel.com |
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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.