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The kernel utilization metric does multiplexing currently and is somewhat
unreliable. The problem is that it uses two instances of the fixed counter,
and the kernel has to multipleplex which causes errors. So should use
CPU_CLK_UNHALTED.THREAD instead.
Before:
# perf stat -M Kernel_Utilization -- sleep 1
Performance counter stats for 'sleep 1':
1,419,425 cpu_clk_unhalted.ref_tsc:k
<not counted> cpu_clk_unhalted.ref_tsc (0.00%)
After:
# perf stat -M Kernel_Utilization -- sleep 1
Performance counter stats for 'sleep 1':
746,688 cpu_clk_unhalted.thread:k # 0.7 Kernel_Utilization
1,088,348 cpu_clk_unhalted.thread
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200309013125.7559-1-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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.