Commit 27dc8653 authored by Simon Marlow's avatar Simon Marlow Committed by Ben Gamari

Edit Debugging/TickyTicky

parent 20318f2a
# Ticky-ticky profiling
Ticky-ticky profiling adds counters to every STG function. It's very low-level, but it really tells you what is going on:
- Add the `-ticky` flag when compiling a Haskell module to enable "ticky-ticky" profiling of that module. This makes GHC emit performance-counting instructions in every STG function.
- Add `-ticky` to the command line when linking, so that you link against a version of the runtime system that allows you to display the results.
- Add `+RTS -rfoo.ticky` to the run-time command line, to put the ticky-ticky profile in the file `foo.ticky`.
It's very low level stuff. You need to use `-ddump-simpl -ddump-prep` when compiling the source files to see the functions that correspond to the performance counter report.
You can mix modules compiled with `-ticky` and modules compiled without.
To really see everything you need to compile all the libraries with `-ticky`. To do that in a standard build tree, here are some flag settings in `build.mk` that work:
```wiki
# Build all libraries with -ticky
GhcLibOpts += -ticky
# Build the RTS in the ticky way
GhcRTSWays += t
# Currently ticky is incompatible with threading
GhcThreaded = NO
# When linking stage2 you need -ticky, else you get unresolved symols
GhcStage2HcOpts += -ticky
# Ditto Haddock
utils/haddock_dist_EXTRA_HC_OPTS += -ticky
```
But see [\#3439](https://gitlab.haskell.org//ghc/ghc/issues/3439), which would allow you to drop the last two.
= Ticky-ticky profiling =
Ticky-ticky profiling adds counters to every STG function. It's very low-level, but it really tells you what is going on:
* Add the `-ticky` flag when compiling a Haskell module to enable "ticky-ticky" profiling of that module. This makes GHC emit performance-counting instructions in every STG function.
* Add `-ticky` to the command line when linking, so that you link against a version of the runtime system that allows you to display the results.
* Add `+RTS -rfoo.ticky` to the run-time command line, to put the ticky-ticky profile in the file `foo.ticky`.
It's very low level stuff. You need to use `-ddump-simpl -ddump-prep` when compiling the source files to see the functions that correspond to the performance counter report.
You can mix modules compiled with `-ticky` and modules compiled without.
To really see everything you need to compile all the libraries with `-ticky`. To do that in a standard build tree, here are some flag settings in `build.mk` that work:
{{{
# Build all libraries with -ticky
GhcLibOpts += -ticky
# Build the RTS in the ticky way
GhcRTSWays += t
# Currently ticky is incompatible with threading
GhcThreaded = NO
# When linking stage2 you need -ticky, else you get unresolved symols
GhcStage2HcOpts += -ticky
# Ditto Haddock
utils/haddock_dist_EXTRA_HC_OPTS += -ticky
}}}
But see #3439, which would allow you to drop the last two.
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