README

This repo is just used to test parsing sql commands to create commands to
add Linux kernel histogram logic:

 (read https://www.kernel.org/doc/Documentation/trace/histogram.rst)

This is a testbed for trace-cmd start --sql '...' commands, which will hopeful
turn into:

 trace-cmd start \
    --sql '(select start.common_timestamp as start_time, end.common_timestamp as end_time, start.pid,
                   (start_time - end_time) as delta
            from sched_waking as start
            join sched_switch as end
              on start.pid = end.next_pid) as first'

Will produce:

 # echo 'first u64 start_time u64 end_time pid_t pid u64 delta' >> synthetic_events 
 # echo 'hist:keys=pid:start=common_timestamp' > events/sched/sched_waking/trigger 
 # echo 'hist:keys=next_pid:start2=$start,delta=common_timestamp-$start:onmatch(sched.sched_waking).trace(first,$start2,common_timestamp,next_pid,$delta)' > events/sched/sched_switch/trigger