6f91ea283a
To stitch LBR call stack, the max LBR information is required. So the CPU PMU capabilities information has to be stored in perf header. Add a new feature HEADER_CPU_PMU_CAPS for CPU PMU capabilities. Retrieve all CPU PMU capabilities, not just max LBR information. Add variable max_branches to facilitate future usage. Committer testing: # ls -la /sys/devices/cpu/caps/ total 0 drwxr-xr-x. 2 root root 0 Apr 17 10:53 . drwxr-xr-x. 6 root root 0 Apr 17 07:02 .. -r--r--r--. 1 root root 4096 Apr 17 10:53 max_precise # # cat /sys/devices/cpu/caps/max_precise 0 # perf record sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.033 MB perf.data (7 samples) ] # # perf report --header-only | egrep 'cpu(desc|.*capabilities)' # cpudesc : AMD Ryzen 5 3600X 6-Core Processor # cpu pmu capabilities: max_precise=0 # And then on an Intel machine: $ ls -la /sys/devices/cpu/caps/ total 0 drwxr-xr-x. 2 root root 0 Apr 17 10:51 . drwxr-xr-x. 6 root root 0 Apr 17 10:04 .. -r--r--r--. 1 root root 4096 Apr 17 11:37 branches -r--r--r--. 1 root root 4096 Apr 17 10:51 max_precise -r--r--r--. 1 root root 4096 Apr 17 11:37 pmu_name $ cat /sys/devices/cpu/caps/max_precise 3 $ cat /sys/devices/cpu/caps/branches 32 $ cat /sys/devices/cpu/caps/pmu_name skylake $ perf record sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.001 MB perf.data (8 samples) ] $ perf report --header-only | egrep 'cpu(desc|.*capabilities)' # cpudesc : Intel(R) Core(TM) i5-7500 CPU @ 3.40GHz # cpu pmu capabilities: branches=32, max_precise=3, pmu_name=skylake $ Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Acked-by: Jiri Olsa <jolsa@redhat.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexey Budankov <alexey.budankov@linux.intel.com> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Pavel Gerasimov <pavel.gerasimov@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com> Cc: Stephane Eranian <eranian@google.com> Cc: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com> Link: http://lore.kernel.org/lkml/20200319202517.23423-3-kan.liang@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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.