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With the hardware TopDown metrics feature, the sample-read feature should be supported for a TopDown group, e.g., sample a non-topdown event and read a Topdown metric group. But the current perf record code errors are out. For a TopDown metric group,the slots event must be the leader of the group, but the leader slots event doesn't support sampling. To support sample-read the TopDown metric group, uses the 2nd event of the group as the "leader" for the purposes of sampling. Only the platform with the TopDown metric feature supports sample-read the topdown group. In commitacb65150a4("perf record: Support sample-read topdown metric group"), it adds arch_topdown_sample_read() to indicate whether the TopDown group supports sample-read, it should only work on the non-hybrid systems, this patch extends the support for hybrid platforms. Before: # ./perf record -e "{cpu_core/slots/,cpu_core/cycles/,cpu_core/topdown-retiring/}:S" -a sleep 1 Error: The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (cpu_core/topdown-retiring/). /bin/dmesg | grep -i perf may provide additional information. After: # ./perf record -e "{cpu_core/slots/,cpu_core/cycles/,cpu_core/topdown-retiring/}:S" -a sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.238 MB perf.data (369 samples) ] Fixes:acb65150a4("perf record: Support sample-read topdown metric group") Reviewed-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Zhengjun Xing <zhengjun.xing@linux.intel.com> Acked-by: Ian Rogers <irogers@google.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20220602153603.1884710-1-zhengjun.xing@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.