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The 'perf record' and 'perf stat' commands have supported the option '-C/--cpus' to count or collect only on the list of CPUs provided. Commit1d3351e631("perf tools: Enable on a list of CPUs for hybrid") add it to be supported for hybrid. For hybrid support, it checks the cpu list are available on hybrid PMU. But when we test only uncore events(or events not in cpu_core and cpu_atom), there is a bug: Before: # perf stat -C0 -e uncore_clock/clockticks/ sleep 1 failed to use cpu list 0 In this case, for uncore event, its pmu_name is not cpu_core or cpu_atom, so in evlist__fix_hybrid_cpus, perf_pmu__find_hybrid_pmu should return NULL,both events_nr and unmatched_count should be 0 ,then the cpu list check function evlist__fix_hybrid_cpus return -1 and the error "failed to use cpu list 0" will happen. Bypass "events_nr=0" case then the issue is fixed. After: # perf stat -C0 -e uncore_clock/clockticks/ sleep 1 Performance counter stats for 'CPU(s) 0': 195,476,873 uncore_clock/clockticks/ 1.004518677 seconds time elapsed When testing with at least one core event and uncore events, it has no issue. # perf stat -C0 -e cpu_core/cpu-cycles/,uncore_clock/clockticks/ sleep 1 Performance counter stats for 'CPU(s) 0': 5,993,774 cpu_core/cpu-cycles/ 301,025,912 uncore_clock/clockticks/ 1.003964934 seconds time elapsed Fixes:1d3351e631("perf tools: Enable on a list of CPUs for hybrid") Reviewed-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Zhengjun Xing <zhengjun.xing@linux.intel.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: alexander.shishkin@intel.com Cc: Andi Kleen <ak@linux.intel.com> Cc: Ian Rogers <irogers@google.com> Cc: Jin Yao <yao.jin@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lore.kernel.org/lkml/20220218093127.1844241-1-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.