maria-discuss team mailing list archive

[Sergey Vojtovich <svoj@xxxxxxxxxxx>]

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