2017-09-26 18:35 GMT+02:00 Ben Gamari
While it's not a bad idea, I think it's easy to drown in information. Of course, it's also fairly easy to hide information that we don't care about, so perhaps this is worth doing regardless.
The point is: You don't know in advance which of the many performance characteristics "perf" spits out is relevant. If e.g. you see a regression in runtime although you really didn't expect one (tiny RTS change etc.), a quick look at the diffs of all perf values can often give a hint (e.g. branch prediction was screwed up by different code layout etc.). So I think it's best to collect all data, but make the user-relevant data (runtime, code size) more prominent than the technical/internal data (cache hit ratio, branch prediction hit ratio, etc.), which is for analysis only. Although the latter is a cause for the former, from a compiler user's perspective it's irrelevant. So there is no actual risk in drowning in data, because you primarily care only for a small subset of it.