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It calculates IPC from the cycles and instruction counts and compares it
with the shadow stat for both global aggregation (default) and no
aggregation mode.
$ perf stat -a -A -e cycles,instructions sleep 1
Performance counter stats for 'system wide':
CPU0 39,580,880 cycles
CPU1 45,426,945 cycles
CPU2 31,151,685 cycles
CPU3 55,167,421 cycles
CPU0 17,073,564 instructions # 0.43 insn per cycle
CPU1 34,955,764 instructions # 0.77 insn per cycle
CPU2 15,688,459 instructions # 0.50 insn per cycle
CPU3 34,699,217 instructions # 0.63 insn per cycle
1.003275495 seconds time elapsed
In this example, the 'insn per cycle' should be matched to the number
for each cpu. For CPU2, 0.50 = 15,688,459 / 31,151,685 .
Committer testing:
# perf test shadow
78: perf stat metrics (shadow stat) test : Ok
#
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20201127041404.390276-2-namhyung@kernel.org
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.