af31fd0c91
Performance Monitoring Unit (PMU) registers in powerpc provides information on cycles elapsed between different stages in the pipeline. This can be used for application tuning. On ISA v3.1 platform, this information is exposed by sampling registers. Patch adds kernel support to capture two of the cycle counters as part of perf sample using the sample type: PERF_SAMPLE_WEIGHT_STRUCT. The power PMU function 'get_mem_weight' currently uses 64 bit weight field of perf_sample_data to capture memory latency. But following the introduction of PERF_SAMPLE_WEIGHT_TYPE, weight field could contain 64-bit or 32-bit value depending on the architexture support for PERF_SAMPLE_WEIGHT_STRUCT. Patches uses WEIGHT_STRUCT to expose the pipeline stage cycles info. Hence update the ppmu functions to work for 64-bit and 32-bit weight values. If the sample type is PERF_SAMPLE_WEIGHT, use the 64-bit weight field. if the sample type is PERF_SAMPLE_WEIGHT_STRUCT, memory subsystem latency is stored in the low 32bits of perf_sample_weight structure. Also for CPU_FTR_ARCH_31, capture the two cycle counter information in two 16 bit fields of perf_sample_weight structure. Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com> Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1616425047-1666-2-git-send-email-atrajeev@linux.vnet.ibm.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.