Performance info gathering?

[conal]

Does HERMIT have any support for gathering performance info? I'm struggling with performance but can only guess at what to tune.

[conal]

I'd also love to hear what techniques people have for profiling (in a broad sense) and improving performance.

[xich]

Do you mean performance of the transformations themselves (i.e. bash)? Or performance of HERMIT (i.e. running a large script)?

[conal]

I guess I'd like to know how much time is spent on which transformations, with info about success rate. But really, I don't know what info would give me the insight I'm looking for about where time is spent and what I can do about it.

[xich]

Hmmm, I haven't really thought about this yet.

I wonder if using the usual SCC pragmas on transformations and compiling with profiling would get anywhere? As always, I'm not sure how this works since we're trying to profile a compiler plugin. I think you'd have to compile GHC itself for profiling?

We could make a facility available to the monad to log events:

class MonadIO m => MonadEvent m where
   logEvent :: String -> m ()

instance MonadEvent HermitM where
   logEvent msg = ... log to a writer the msg and time ...

instance MonadEvent m => MonadEvent (Transform c m a) where
   logEvent = constT . logEvent

-- semantically an identity, with side effect of logging start and end times
timeT :: MonadEvent m => String -> Transform c m a b -> Transform c m a b
timeT nm t = logEvent ("start " ++ nm) >> t >>= \r -> logEvent ("end " ++ nm) >> return r

Then you could take the event log and parse and accumulate cost centers. Something like that?