Explicitly setting thread_cache_size=-1 (autosizing) doesn't work

[Thomas Deutschmann]

Server version: 5.6.29-76.2 Percona Server (GPL), Release 76.2, Revision ddf26fe on Debian Wheezy from Percona repository

I've set "thread-cache-size=-1" in my.cnf which should cause an automatic value for thread_cache_size according to http://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_thread_cache_size

However when set to "-1":

mysql> SHOW VARIABLES LIKE "thread_cache_size";
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| thread_cache_size | 0 |
+-------------------+-------+
1 row in set (0.00 sec)

When I manually set a positive value (thread-cache-size=7) it will work:
mysql> SHOW VARIABLES LIKE "thread_cache_size";
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| thread_cache_size | 7 |
+-------------------+-------+
1 row in set (0.00 sec)

When I remove the declaration from my.cnf so that MySQL's default will be used and set max_connections=800 (to test the formula '8 + (max_connections / 100)') everything works, too:
mysql> SHOW VARIABLES LIKE "thread_cache_size";
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| thread_cache_size | 16 |
+-------------------+-------+
1 row in set (0.00 sec)

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-3408