mysql select count long query time : 3 million table records, select count query time is 0.6 seconds

3.2 million table records, select count query time is 8.4 seconds (200,000 new records)

3 million table records, select count query time is 8.4 seconds (delete 200,000 records)

1.2 million table records, select count query time is 9.7 seconds (more than 200,000 records deleted)

Data are normal when they are less than 3 million.
Insert 200,000 data at a time, execute multiple times, and delete tests. Mysql5.6, windows10 


    select count(1) from t_node;
    delete from t_Node limit 200000;
    insert into t_node select * from t_node limit 200000;



i want select count query time < 1s

