performance testing

Hi all, I'm very confused by how to do performance testing. I have a patch that seems to cause a performance regression. So I built the patch locally (`validate` flavor, with `make`) and then reproduced the regression. Good. Then, I make a small change, rebuild, commit, and then test. But now it seems that the baseline has changed. (This took some time to discover after seemingly non-deterministic results!) So: how can I make several different commits, with different experiments, switch between them at will, all without changing my baseline? I do *not* have the magic "metric decrease" bit in my commit message. Or, at least, I didn't put it there. Thanks! Richard