qcache.pl

#!/usr/bin/perl

use strict;
use warnings;
use DBI;
use Time::HiRes;
use Parallel::ForkManager;

my $dsn= "dbi:mysql:d1;mysql_socket=/tmp/mysql.sock";
my $pm = Parallel::ForkManager->new(10);

while ()
{
  my $pid = $pm->start and next;
  my $conn= DBI->connect($dsn, "root", "");

  while ()
  {
    $conn->do("SELECT 1 FROM t1 WHERE val = ? OR val = ?", undef, Time::HiRes::time(), $pid);
  }

  $pm->finish;
}

exit 0;

result

mysql> SET GLOBAL query_cache_type= 1;
Query OK, 0 rows affected (0.00 sec)

### run qcache.pl ###

mysql> show processlist;
+-------+------+-----------+------+---------+------+------------------------------+--------------------------------------------------------------+
| Id    | User | Host      | db   | Command | Time | State                        | Info                                                         |
+-------+------+-----------+------+---------+------+------------------------------+--------------------------------------------------------------+
| 54679 | root | localhost | d1   | Query   |    0 | starting                     | show processlist                                             |
| 54690 | root | localhost | d1   | Query   |    0 | Waiting for query cache lock | SELECT 1 FROM t1 WHERE val = '1425864656.15922' OR val = '0' |
| 54691 | root | localhost | d1   | Query   |    0 | Waiting for query cache lock | SELECT 1 FROM t1 WHERE val = '1425864656.16056' OR val = '0' |
| 54692 | root | localhost | d1   | Query   |    0 | Writing to net               | SELECT 1 FROM t1 WHERE val = '1425864656.16157' OR val = '0' |
| 54693 | root | localhost | d1   | Query   |    0 | Waiting for query cache lock | SELECT 1 FROM t1 WHERE val = '1425864656.16253' OR val = '0' |
| 54694 | root | localhost | d1   | Query   |    0 | freeing items                | SELECT 1 FROM t1 WHERE val = '1425864656.16162' OR val = '0' |
| 54695 | root | localhost | d1   | Query   |    0 | Waiting for query cache lock | SELECT 1 FROM t1 WHERE val = '1425864656.1633' OR val = '0'  |
| 54696 | root | localhost | d1   | Sleep   |    0 |                              | NULL                                                         |
| 54697 | root | localhost | d1   | Query   |    0 | Writing to net               | SELECT 1 FROM t1 WHERE val = '1425864656.16509' OR val = '0' |
| 54698 | root | localhost | d1   | Query   |    0 | Writing to net               | SELECT 1 FROM t1 WHERE val = '1425864656.16422' OR val = '0' |
| 54699 | root | localhost | d1   | Query   |    0 | Waiting for query cache lock | SELECT 1 FROM t1 WHERE val = '1425864656.16234' OR val = '0' |
+-------+------+-----------+------+---------+------+------------------------------+--------------------------------------------------------------+
11 rows in set (0.00 sec)

schema

mysql> show create table t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE `t1` (
  `num` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `val` varchar(32) DEFAULT NULL,
  UNIQUE KEY `num` (`num`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8
1 row in set (0.02 sec)

mysql>
mysql> SELECT * FROM t1;
+-----+------+
| num | val  |
+-----+------+
|   1 | one  |
|   2 | two  |
+-----+------+
2 rows in set (0.00 sec)