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On systems with many CPUs, recording extra context switch events can be
excessive and unnecessary. Add perf config intel-pt.all-switch-events=false
to control the behaviour.
Example:
# perf config intel-pt.all-switch-events=false
# perf record -eintel_pt//u uname
Linux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.082 MB perf.data ]
# perf script -D | grep PERF_RECORD_SWITCH | awk '{print $5}' | uniq -c
5 PERF_RECORD_SWITCH
# perf config intel-pt.all-switch-events=true
# perf record -eintel_pt//u uname
Linux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.102 MB perf.data ]
# perf script -D | grep PERF_RECORD_SWITCH | awk '{print $5}' | uniq -c
180 PERF_RECORD_SWITCH_CPU_WIDE
Committer testing:
While doing a make -j28 allmodconfig:
root@five:~# grep "model name" -m1 /proc/cpuinfo
model name : Intel(R) Core(TM) i7-14700K
root@five:~#
root@five:~# perf config intel-pt.all-switch-events=false
root@five:~# perf record -e intel_pt//u uname
Linux
[ perf record: Woken up 2 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data ]
root@five:~# perf report --stats | grep SWITCH_CPU_WIDE
root@five:~#
root@five:~# perf config intel-pt.all-switch-events=true
root@five:~# perf record -e intel_pt//u uname
Linux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.047 MB perf.data ]
root@five:~# perf report --stats | grep SWITCH_CPU_WIDE
SWITCH_CPU_WIDE events: 542 (96.4%)
root@five:~#
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250512093932.79854-3-adrian.hunter@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 reStructuredText 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.