Last month we did a few improvements in InnoDB memory usage. We solved a challenging issue about how InnoDB uses memory in certain places of the code.
The symptom of the issue was that under a certain workloads the memory used by InnoDB kept growing infinitely, until OOM killer kicked in. It looked like a memory leak, but Valgrind wasn’t reporting any leaks and the issue was not reproducible on FreeBSD – it only happened on Linux (see Bug#57480). Especially the latest fact lead us to think that there is something in the InnoDB memory usage pattern that reveals a nasty side of the otherwise good-natured Linux’s memory manager.
It turned out to be an interesting …[Read more]