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authorThomas Richter <tmricht@linux.ibm.com>2018-06-15 12:11:05 +0200
committerArnaldo Carvalho de Melo <acme@redhat.com>2018-06-25 11:59:37 -0300
commit6dde6429c5ff5b38d6d40a14a6ee105117e6364d (patch)
tree1a15fc00cee2ecafdc4a74297ce069e1af0c04c1 /tools/perf/bench
parent0c24d6fb7bd3578e5b9e4972d01bbe3d087ded33 (diff)
perf stat: Remove duplicate event counting
'perf stat' shows a mismatch in perf stat regarding counter names on s390: Run command: [root@s35lp76 perf]# ./perf stat -e tx_nc_tend -v -- ~/mytesttx 1 >/tmp/111 tx_nc_tend: 1 573146 573146 tx_nc_tend: 1 573146 573146 Performance counter stats for '/root/mytesttx 1': 3 tx_nc_tend 0.001037252 seconds time elapsed [root@s35lp76 perf]# shows transaction counter tx_nc_tend with value 3 but it was triggered only once as seen by the output of mytesttx. When looking up the event name tx_nc_tend the following function sequence is called: parse_events_multi_pmu_add() +--> perf_pmu__scan() being called with NULL argument +--> pmu_read_sysfs() scans directory ../devices/ for all PMUs +--> perf_pmu__find() tries to find a PMU in the global pmu list. +--> pmu_lookup() called to read all file entries when not in global list. pmu_lookup() causes the issue. It calls +---> pmu_aliases() to read all the entries in the PMU directory. On s390 this is named /sys/devices/cpum_cf/events. +--> pmu_aliases_parse() reads all files and creates an alias for each file name. So we end up with first entry created by reading the sysfs file [root@s35lp76 perf]# cat /sys/devices/cpum_cf /events/TX_NC_TEND event=0x008d [root@s35lp76 perf]# Debug output shows this entry tx_nc_tend -> 'cpum_cf'/'event=0x008d '/ After all files in this directory have been read and aliases created this function is called: +--> pmu_add_cpu_aliases() This function looks up the CPU tables created by the json files. With json files for s390 now available all the aliases are added to the PMU alias list a second time. The second entry is added by reading the json file converted by jevent resulting in file pmu-events/pmu-events.c: { .name = "tx_nc_tend", .event = "event=0x8d", .desc = "Unit: cpum_cf Completed TEND \ instructions \ in non-constrained TX mode", .topic = "extended", .long_desc = "A TEND instruction has \ completed in a \ non-constrained \ transactional-execution mode", .pmu = "cpum_cf", }, Debug output shows this entry tx_nc_tend -> 'cpum_cf'/'event=0x8d'/ Function pmu_aliases_parse() and pmu_add_cpu_aliases() both use __perf_pmu__new_alias() to add an alias to the PMU alias list. There is no check if an alias already exist So we end up with 2 entries for tx_nc_tend in the PMU alias list. Having set up the PMU alias list for this PMU now parse_events_multi_add_pmu() reads the complete alias list and adds each alias with parse_events_add_pmu() to the global perfev_list. This causes the alias to be added multiple times to the event list. Fix this by making __perf_pmu__new_alias() to merge alias definitions if an alias is already on the alias list. Also print a debug message when the alias has mismatches in some fields. Output before: [root@s35lp76 perf]# ./perf stat -e tx_nc_tend -v \ -- ~/mytesttx 1 >/tmp/111 tx_nc_tend: 1 551446 551446 Performance counter stats for '/root/mytesttx 1': 3 tx_nc_tend 0.000961134 seconds time elapsed [root@s35lp76 perf]# Output after: [root@s35lp76 perf]# ./perf stat -e tx_nc_tend -v \ -- ~/mytesttx 1 >/tmp/111 tx_nc_tend: 1 551446 551446 Performance counter stats for '/root/mytesttx 1': 1 tx_nc_tend 0.000961134 seconds time elapsed [root@s35lp76 perf]# Signed-off-by: Thomas Richter <tmricht@linux.ibm.com> Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com> Reviewed-by: Jiri Olsa <jolsa@redhat.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Link: http://lkml.kernel.org/r/20180615101105.47047-3-tmricht@linux.ibm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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