HIST_STACKTRACE_SIZE  288 kernel/trace/trace_events_hist.c #define HIST_KEY_SIZE_MAX	(MAX_FILTER_STR_VAL + HIST_STACKTRACE_SIZE)
HIST_STACKTRACE_SIZE 5372 kernel/trace/trace_events_hist.c 			memset(entries, 0, HIST_STACKTRACE_SIZE);