Profiteur: a visualiser for Haskell GHC .prof files

Posted in: haskell.

Introduction

GHC comes with some amazing tools to do profiling of Haskell programs. In .prof files, you can see exactly in which function most time is spent and where most allocation is done.

However, at Erudify, we have a huge amount of Haskell code – and at this point .prof files can become very unwieldy, and the text representation is harder to grok.

This is why I coded profiteur, a simple HTML-based visualiser for GHC .prof files.

Screenshot of profiteur

Screenshot of profiteur

Installation

Installation is easy:

$ cabal install profiteur

Usage

Let us grab a sample program from the HaskellWiki. The code of this sample program can be found in the appendix. I saved this file as binary-trees.hs.

First, we compile it with profiling enabled:

$ ghc --make -auto-all -prof -rtsopts binary-trees.hs
[1 of 1] Compiling Main             ( binary-trees.hs, binary-trees.o )
Linking binary-trees ...

We run it in profiling mode:

$ ./binary-trees 10 +RTS -p -RTS
stretch tree of depth 11     check: -1
2048     trees of depth 4    check: -2048
512  trees of depth 6    check: -512
128  trees of depth 8    check: -128
32   trees of depth 10   check: -32
long lived tree of depth 10  check: -1

This generates the file binary-trees.prof. We can pass that to profiteur:

$ profiteur binary-trees.prof
Wrote binary-trees.prof.html

Open the resulting file in your favorite (modern) browser and you are good to go! Here is the resulting HTML file so you can have a look without installing profiteur.

As always, patches and pull requests are welcome on GitHub.

Appendix

Code used:

{-# LANGUAGE BangPatterns #-}
{-# OPTIONS_GHC -funbox-strict-fields #-}
--
-- The Great Computer Language Shootout
-- http://shootout.alioth.debian.org/
--
-- Contributed by Don Stewart
--
 
import System.Environment
import Data.Bits
import Text.Printf
 
data Tree = Nil | Node !Int Tree Tree
 
minN = 4
 
io s !n !t = printf "%s of depth %d\t check: %d\n" s n t
 
main = do
    n <- getArgs >>= readIO . head
    let maxN     = max (minN + 2) n
        stretchN = maxN + 1
 
    -- stretch memory tree
    let c = check (make 0 stretchN)
    io "stretch tree" stretchN c
 
    -- allocate a long lived tree
    let long    = make 0 maxN
 
    -- allocate, walk, and deallocate many bottom-up binary trees
    let vs = depth minN maxN
    mapM_ (\((m,d,i)) -> io (show m ++ "\t trees") d i) vs
 
    -- confirm the the long-lived binary tree still exists
    io "long lived tree" maxN (check long)
 
-- generate many trees
depth :: Int -> Int -> [(Int,Int,Int)]
depth !d !m
    | d <= m    = (2*n,d,sumT d n 0) : depth (d+2) m
    | otherwise = []
  where !n = 1 `shiftL` (m - d + minN)
 
-- allocate and check lots of trees
sumT :: Int -> Int -> Int -> Int
sumT !d 0 t = t
sumT  d i t = sumT d (i-1) (t + a + b)
  where a = check (make i    d)
        b = check (make (-i) d)
 
-- traverse the tree, counting up the nodes
check :: Tree -> Int
check Nil          = 0
check (Node i l r) = i + check l - check r
 
-- build a tree
make :: Int -> Int -> Tree
make i 0 = Node i Nil Nil
make i d = Node i (make (i2-1) d2) (make i2 d2)
  where i2 = 2*i; d2 = d-1

Comments

ce0f13b2-4a83-4c1c-b2b9-b6d18f4ee6d2