As you probably have experienced yet MySQL does not always provide all internal information as you might want to have them and as you are used to have from other RDBMS.
MySQL plans to improve this implementing the/a performance schema and its probably already partly done in MySQL 5.4. But who knows when this will be finished and what it contains at all...
What is not provided to me I want to gather myself... But how? Other RDBMS provide interfaces to attach applications directly to their memory to retreive information. But MySQL does not. So I was looking for a way to read an other process memory.
I have no clue about programming and thus changing MySQL code was out of focus. Further I am looking for a solution you can use immediately on a running systems at consulting gigs. Some tries to read /proc/<pid>/mem with a little php script failed.
An article by Domas M. helped me. I do not have to write something myself I can use a tool already exsting to do the work. But gdb is not installed on every machine and usually not at all on production machines. Further gdb is probably an overkill to just read memory of other processes.
But an other application to do this job I did not find. I just found some comments that ptrace is the way to do it. Ptrace (man ptrace) is not a program (as for example strace) but an operating system function call.
When you are interested how I found out how to do it please continue reading here.