Mysql – Why are the queries getting really slow

I own a WordPress installation, and Updated to 3.4.1.

After the upgrade, I experienced a very strange slow-down.

After all, I used the

define('SAVEQUERIES', true);

in my wp-config.php with combined with the following code in my theme footer.php

global $wpdb;
echo "<pre>";
print_r($wpdb->queries);
echo "</pre>";

and I found that while I don't have many queries (49 queries I got), there are

• 4 Queries took more than 9''
• 3 Queries took more than 8''
• 4 Queries took more than 7''
• 4 Queries took more than 6''
• 8 Queries took more than 5''
• 1 Query took more than 4''

Here I will show you some of the queries:

/* Execution time 7.0095062E-5 */
SELECT t.*, tt.* FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN ('category') AND tt.count > 0 ORDER BY t.name ASC

/* Execution time 5.3167343E-5 */
SELECT post_id, meta_key, meta_value FROM wp_postmeta WHERE post_id IN (77375,77379,77381)

/* Execution time 9.2029572E-5 */
SELECT wp_posts.* FROM wp_posts WHERE ID IN (77381,77379,77375)

In most of the queries, the query is simple, with no complexity. I cannot imagine why the queries are so slow.

The WordPress database contains in about 60,000 records and running on Percona-Server.

Any ideas for for what the issue might be, and how I could fix it ?