mysql-test-run consumes much more resources in 5.5 compared to 5.3.
In 5.3 I was able to run the entire test suite (with --mem --parallel=10) in around 6 minutes on a machine with 8GB of memory. 3 min for a release build.
In 5.5 it takes much longer. And worse, we see failures on hosts due to consuming too much resource. Eg. the DGCov builder in buildbot ran out of memory just using --mem --parallel=2, with 3GB of memory available.
It still needs to be quantified more precisely what the problems are. Possibilities include
- Writing too large files in mysql-test/var/, overflowing memory
- safemalloc overhead
- unit tests being included in mtr (f.ex. some of the aria unit tests consume huge amount of resources)
- something else entirely