Hello Omer, I don't quite understand; is +RTS -hc what you want? That will output a heap profile per cost center, which will give you residency. Is the problem that you need a heap profile every minor GC rather than major GC (e.g. something like https://ghc.haskell.org/trac/ghc/ticket/8504 ?) Edward Excerpts from Ömer Sinan Ağacan's message of 2016-08-08 11:28:48 +0000:

One thing that we can't currently see in cost center reports is the residency and because of that cost centers can't be used for fixing memory leaks or reducing max. memory residency. For example, I can have a function that returns an `Int` but allocates lots of intermediate data on the way. In the reports I see this function as allocates a lot, but it has no effect on my program's residency (especially if it runs fast).

So I'm thinking of somehow using cost centers for reasoning about memory residency. One idea is to print a summary after every major GC, by doing another pass on the whole heap and recording attributions. This can be used for plotting live data of cost centers over time. (like hp2ps but for cost centers)

Another idea is to add "residency" column in the profiling reports. Not sure how to update this column in runtime though.

The main use case for me is fixing T1969, but of course this is a very general solution.

Does anyone have any other ideas?