Using c + + to connect mysql, execute queries 30000 times, the program run a probably around 30 s, but two this program run at the same time, it takes around 60 s to both programs, and CPU is doubled, but it didn't achieve the result of concurrent query, in addition, the query whether the program with the mysql server on a single machine performance gap is very big, on the same machine at about 30 s, different machines and about 110 seconds, strives for the great god answer