InnoDB tablespace usage monitor
A really simple tool that would report the amount of innodb tablespace used by specific tables and, ideally, indexes too.
This is required as I'm fairly sure that there isn't a tool to do this at the moment.
MyISAM mmap() its index files
I'm having trouble tuning MyISAM's key_buffer for production use. We want to use delay_key_write to reduce the IO of a lot of inserts, but at the same time, I'd prefer it not to get too out of hand, as large flushes create a lot of I/O in one go.
Anyway perhaps that was a poor explanation of my motivation, however, the idea would be:
- mmap() the whole of each index file when the table is opened.
- Leave the memory mapping in place as long as the table is open. resize the file and the memory mapping if necessary, e.g. when the index file gets bigger.
- Have all reads/writes go via the memory mapping.
- msync() as necessary (e.g. following a write)
I'm confident that this will have a performance benefit, but mostly, it will remove the onus on the DBA to tune key_buffer correctly, and allow the OS to use its memory how it wants to.
The downside? It won't work very well on 32-bit systems as they'll rapidly run out of address space. But do we care any more?