Adds a test for a counter obtained using read() system call during
multiplexing.

  $ sudo make tests -C ./tools/lib/perf/ V=1
  make: Entering directory '/home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/lib/perf'
  make -f /home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/build/Makefile.build dir=. obj=libperf
  make -C /home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/lib/api/ O= libapi.a
  make -f /home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/build/Makefile.build dir=./fd obj=libapi
  make -f /home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/build/Makefile.build dir=./fs obj=libapi
  make -f /home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/build/Makefile.build dir=. obj=tests
  make -f /home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/build/Makefile.build dir=./tests obj=tests
  running static:
  - running tests/test-cpumap.c...OK
  - running tests/test-threadmap.c...OK
  - running tests/test-evlist.c...
  Event  0 -- Raw count = 298049842, run = 270269503, enable = 456262127
           Scaled count = 503160191 (59.24%, 270269503/456262127)
  Event  1 -- Raw count = 299134173, run = 271075173, enable = 456257234
           Scaled count = 503484435 (59.41%, 271075173/456257234)
  Event  2 -- Raw count = 300461996, run = 272069283, enable = 456253417
           Scaled count = 503867290 (59.63%, 272069283/456253417)
  Event  3 -- Raw count = 301308704, run = 273063387, enable = 456249352
           Scaled count = 503443183 (59.85%, 273063387/456249352)
  Event  4 -- Raw count = 302531164, run = 274102932, enable = 456244712
           Scaled count = 503563543 (60.08%, 274102932/456244712)
  Event  5 -- Raw count = 303710254, run = 275406214, enable = 456228165
           Scaled count = 503115633 (60.37%, 275406214/456228165)
  Event  6 -- Raw count = 304531302, run = 276396076, enable = 456221130
           Scaled count = 502661313 (60.58%, 276396076/456221130)
  Event  7 -- Raw count = 304486460, run = 276601890, enable = 456213754
           Scaled count = 502205212 (60.63%, 276601890/456213754)
  Event  8 -- Raw count = 304116681, run = 276631326, enable = 456205562
           Scaled count = 501532936 (60.64%, 276631326/456205562)
  Event  9 -- Raw count = 303567766, run = 276188567, enable = 456196839
           Scaled count = 501420666 (60.54%, 276188567/456196839)
  Event 10 -- Raw count = 302238014, run = 275144001, enable = 456185300
           Scaled count = 501106833 (60.31%, 275144001/456185300)
  Event 11 -- Raw count = 300805716, run = 273824589, enable = 456175608
           Scaled count = 501124573 (60.03%, 273824589/456175608)
  Event 12 -- Raw count = 299959051, run = 272834556, enable = 456166593
           Scaled count = 501517477 (59.81%, 272834556/456166593)
  Event 13 -- Raw count = 299037090, run = 271820805, enable = 456157086
           Scaled count = 501830195 (59.59%, 271820805/456157086)
  Event 14 -- Raw count = 298327042, run = 270784311, enable = 456147546
           Scaled count = 502544433 (59.36%, 270784311/456147546)
     Expected: 501614268
     High: 503867290   Low:  298049842   Average:  502438527
     Average Error = 0.16%
  OK
  - running tests/test-evsel.c...
          loop = 65536, count = 328182
          loop = 131072, count = 660214
          loop = 262144, count = 1315534
          loop = 524288, count = 2635364
          loop = 1048576, count = 5271971
          loop = 65536, count = 491952
          loop = 131072, count = 850061
          loop = 262144, count = 1648608
          loop = 524288, count = 3162059
          loop = 1048576, count = 6353393
  OK
  running dynamic:
  - running tests/test-cpumap.c...OK
  - running tests/test-threadmap.c...OK
  - running tests/test-evlist.c...
  Event  0 -- Raw count = 300218292, run = 297528154, enable = 496789343
           Scaled count = 501281125 (59.89%, 297528154/496789343)
  Event  1 -- Raw count = 301438606, run = 298515328, enable = 496784768
           Scaled count = 501649643 (60.09%, 298515328/496784768)
  Event  2 -- Raw count = 302342618, run = 298798983, enable = 496782015
           Scaled count = 502673648 (60.15%, 298798983/496782015)
  Event  3 -- Raw count = 303132319, run = 299230407, enable = 496778508
           Scaled count = 503256412 (60.23%, 299230407/496778508)
  Event  4 -- Raw count = 302758195, run = 299218047, enable = 496774243
           Scaled count = 502651743 (60.23%, 299218047/496774243)
  Event  5 -- Raw count = 303158458, run = 299204274, enable = 496769146
           Scaled count = 503334281 (60.23%, 299204274/496769146)
  Event  6 -- Raw count = 303471397, run = 299197479, enable = 496763124
           Scaled count = 503859189 (60.23%, 299197479/496763124)
  Event  7 -- Raw count = 303583387, run = 299196861, enable = 496756458
           Scaled count = 504039405 (60.23%, 299196861/496756458)
  Event  8 -- Raw count = 303096897, run = 299186924, enable = 496748667
           Scaled count = 503240507 (60.23%, 299186924/496748667)
  Event  9 -- Raw count = 301424173, run = 297845086, enable = 496739994
           Scaled count = 502709122 (59.96%, 297845086/496739994)
  Event 10 -- Raw count = 300876415, run = 296851339, enable = 496729034
           Scaled count = 503464297 (59.76%, 296851339/496729034)
  Event 11 -- Raw count = 300239338, run = 296547963, enable = 496719538
           Scaled count = 502902612 (59.70%, 296547963/496719538)
  Event 12 -- Raw count = 299751948, run = 296547195, enable = 496710036
           Scaled count = 502077926 (59.70%, 296547195/496710036)
  Event 13 -- Raw count = 299341883, run = 296549981, enable = 496700423
           Scaled count = 501376663 (59.70%, 296549981/496700423)
  Event 14 -- Raw count = 299145476, run = 296561684, enable = 496690949
           Scaled count = 501018366 (59.71%, 296561684/496690949)
     Expected: 501669431
     High: 504039405   Low:  300218292   Average:  502635662
     Average Error = 0.19%
  OK
  - running tests/test-evsel.c...
          loop = 65536, count = 329275
          loop = 131072, count = 664638
          loop = 262144, count = 1315367
          loop = 524288, count = 2629617
          loop = 1048576, count = 5273657
          loop = 65536, count = 459641
          loop = 131072, count = 978402
          loop = 262144, count = 1581219
          loop = 524288, count = 3774908
          loop = 1048576, count = 7694417
  OK
  make: Leaving directory '/home/nakamura/build_work/build_kernel/linux_kernel/linux/tools/lib/perf'
Signed-off-by: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211109085831.3770594-4-nakamura.shun@fujitsu.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>