Documentation/trace/histogram-design.rst

38   # echo 'hist:keys=pid' >> events/sched/sched_waking/trigger
42   { pid:      18249 } hitcount:          1
43   { pid:      13399 } hitcount:          1
44   { pid:      17973 } hitcount:          1
45   { pid:      12572 } hitcount:          1
47   { pid:         10 } hitcount:        921
48   { pid:      18255 } hitcount:       1444
49   { pid:      25526 } hitcount:       2055
50   { pid:       5257 } hitcount:       2055
51   { pid:      27367 } hitcount:       2055
52   { pid:       1728 } hitcount:       2161
60 pid as a key and with a single value, hitcount, which even if not
65 pid.
67 So in this histogram, there's a separate bucket for each pid, and each
69 sched_waking was called for that pid.
105 for the hitcount and one key field for the pid key.
127                            | key = pid      |----------------------------|--+
184                       | .key    |---> pid = 999                          |  |
206                       | .key    |---> pid = 4444                         |  |
241 is just one subkey corresponding to pid), the hist_field that
360 pid, and later a sched_switch event that switches to that pid event
364   # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >>
416                          | key = pid         |                            | | |
483                       | .key    |---> pid = 999                           | | |
527                       | .key    |---> pid = 4444                          | | |
571 pid 999 is 113345679876, and the timestamp variable in the same             | |
572 .var.idx for pid 4444 is 213499240729.                                      | |
642  |                     | | key = pid             |                          | |
726   # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
743 …# trigger info: hist:keys=pid:vals=hitcount:ts0=common_timestamp.usecs:sort=hitcount:size=2048:clo…
775       ftrace_event_field name: pid
854   # echo '!hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
865 case if we have a pid in the sched_waking histogram that matches the
894   # echo 'wakeup_latency u64 lat; pid_t pid' >> synthetic_events
898   # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >>
973    || +--------------+ | | | key = pid             |
1102   # echo 'wakeup_latency u64 lat; pid_t pid; char comm[16]' >> synthetic_events
1106   # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
1124 …# trigger info: hist:keys=pid:vals=hitcount:ts0=common_timestamp.usecs:sort=hitcount:size=2048:clo…
1156       ftrace_event_field name: pid
1310   # echo '!hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
1312   # echo '!wakeup_latency u64 lat; pid_t pid; char comm[16]' >> synthetic_events
1385   # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
1400 …# trigger info: hist:keys=pid:vals=hitcount:ts0=common_timestamp.usecs:sort=hitcount:size=2048:clo…
1432       ftrace_event_field name: pid
1607   # echo '!hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
1632   # echo 'wakeup_latency u64 lat; pid_t pid; int prio' >> synthetic_events
1636   # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
1671 …# trigger info: hist:keys=pid:vals=hitcount:ts0=common_timestamp.usecs:sort=hitcount:size=2048:clo…
1703       ftrace_event_field name: pid
1711   # trigger info: hist:keys=pid:vals=hitcount:synthetic_prio=prio:sort=hitcount:size=2048 [active]
1744       ftrace_event_field name: pid
1868   # echo '!hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
1870   # echo '!wakeup_latency u64 lat; pid_t pid; int prio' >> synthetic_events
1880   # echo 'wakeup_latency u64 lat; pid_t pid; char comm[16]' >> synthetic_events
1883 but in this case we save the pid in the waking_pid variable::
1885 …# echo 'hist:keys=pid:waking_pid=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trig…
1901 …# trigger info: hist:keys=pid:vals=hitcount:waking_pid=pid,ts0=common_timestamp.usecs:sort=hitcoun…
1922       ftrace_event_field name: pid
1943       ftrace_event_field name: pid
2113   # echo '!hist:keys=pid:ts0=common_timestamp.usecs' >> events/sched/sched_waking/trigger
2115   # echo '!wakeup_latency u64 lat; pid_t pid; char comm[16]' >> synthetic_events