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unsigned long int g_tx_port[16] = {0};
/*******
speed: 1Mb is 1*1000*1000bit
bytes: tx pkt bytes
*******/
int speed_limit(unsigned long speed, int port_id, unsigned int bytes)
{
	unsigned long cycles_speed = speed / HZ;
	unsigned long diff_cycles = 0;
	unsigned long cur_cycles = 0;
	static unsigned long last_tsc[16] = {0};
	
	cur_cycles = jiffies;
	if(last_tsc[port_id] == 0)
	{
		last_tsc[port_id] = cur_cycles;
		g_tx_port[port_id] = cycles_speed;
		goto label;
	}

	diff_cycles  = cur_cycles - last_tsc[port_id];
	last_tsc[port_id] = cur_cycles;
	
	g_tx_port[port_id] += cycles_speed  * diff_cycles;
	if(g_tx_port[port_id] > speed)
	{
		g_tx_port[port_id] = speed;
	}
	
	while(g_tx_port[port_id] < bytes * 8)
	{
		cur_cycles = jiffies;
		diff_cycles  = cur_cycles - last_tsc[port_id];
		last_tsc[port_id] = cur_cycles;

		g_tx_port[port_id] += cycles_speed  * diff_cycles;
		if(g_tx_port[port_id] > speed)
		{
			g_tx_port[port_id] = speed;
		}
	}
	
	g_tx_port[port_id] -= bytes * 8;
label:
	return 0;
}