#! /usr/bin/env stap

# This script displays the top 10 most shared locks, i.e. locks which are
# accessed by multiple different threads.
# Example output:
# Tracing pid 8874
# ^Clock	#threads	acquisitions
# 0x0000000002531d90	8	8
# 0x0000000002652650	5	120
# 0x000000000259d2c8	5	5396
# 0x000000000259cb20	5	2588
# 0x000000000259ca00	5	6
# 0x000000000263a7f0	3	26
# 0x0000000002637ba8	3	219
# 0x0000000002637aa0	3	106
# 0x0000000002637700	3	135
# 0x00000000025b7af0	3	1005


global lock_thread_dist 	# map[lock, thread] = count
global top10


probe begin {
	if (target() == 0) {
		println("Target pid or process needed.")
		exit()
	}
	printf("Tracing pid %d\n", target())
}

probe end {
	count=0
	sum=0
	lock=0
	foreach ([l-, t] in lock_thread_dist) {
		if (lock != l) {
			if (lock != 0)
				top10[lock, count] = sum
			lock = l
			count = 0
			sum = 0
		}
		count++
		sum += @count(lock_thread_dist[l,t])
	}
	println("lock\t#threads\tacquisitions")
	foreach ([l, c-] in top10 limit 10)
		printf("%p\t%d\t%d\n", l, c, top10[l,c])
}

probe process("/lib64/libpthread.so.0").mark("mutex_acquire") {
	lock_thread_dist[$arg1, tid()] <<< 1
}