Hi Jean, On Wed, Apr 22, 2015 at 12:31:56AM +0200, Jean Weisbuch wrote:
There was also a MDEV created about this very problem on MariaDB by Guillaume : https://mariadb.atlassian.net/browse/MDEV-7292
But in my opinion, this specific test is only usefull to see scalability issues or the cache warming impact but it doesnt really reflect a typical real-world usage (the original topic here) : if you use this cache its because you wont always query different tables but eventually have queries on tables already cached.
I wonder what is the performance difference when the cache is warm and all tables are already in cache vs. a way too limited table cache that will have to purge LRU tables frequently. Among other expensive things table definition cache miss (as well as eviction) does I/O. So it is a lot more expensive than table cache hit. How much? That depends on workload.
Regards, Sergey