On Fri, Feb 15, 2013 at 10:05 AM, Nicolas Frisby <nicolas.frisby@gmail.com> wrote:

I'm way below my depth here, but I'd like to use the perf tool to see where a program is spending its time.

 

Unfortunately, the recipe here

 

http://hackage.haskell.org/trac/ghc/wiki/Debugging/LowLevelProfiling/Perf

 

isn't working for me. I get output like this instead

 

90.20%  drbg_test  drbg_test          [.] 0x2515ef
  5.71%  drbg_test  [kernel.kallsyms]  [k] 0xffffffff8103e0ca
  1.53%  drbg_test  libc-2.15.so       [.] bsearch
  1.02%  drbg_test  libc-2.15.so       [.] 0x9194c
  0.43%  drbg_test  libgmp.so.10.0.2   [.] __gmpz_mul_2exp
  0.27%  drbg_test  libgmp.so.10.0.2   [.] __gmpz_add
  0.16%  drbg_test  [vdso]             [.] 0x7fffd3d25983
  0.16%  drbg_test  libgmp.so.10.0.2   [.] __gmpn_lshift
  0.10%  drbg_test  libgmp.so.10.0.2   [.] 0x13565
  0.05%  drbg_test  libgmp.so.10.0.2   [.] __gmpz_init
  0.05%  drbg_test  libc-2.15.so       [.] __select
  0.05%  drbg_test  libgmp.so.10.0.2   [.] __gmpn_modexact_1_odd
  0.05%  drbg_test  libgmp.so.10.0.2   [.] __gmpz_realloc
  0.05%  drbg_test  libc-2.15.so       [.] __errno_location
  0.05%  drbg_test  drbg_test          [.] __gmpz_init@plt
  0.05%  drbg_test  librt-2.15.so      [.] clock_gettime
  0.05%  drbg_test  libgmp.so.10.0.2   [.] __gmpn_add_n

 

Again --- below my depth here --- but I don't know how to investigate what 0x2515ef indicates. Does anyone have any pointers?

 

I was hoping that the address would be a nice RTS-ish symbol, like in the Wiki's examples.

I thought I fixed this issue (at least in the native backend). What was missing before was .size assembler directives that would let tools like perf know where a function started and ended. See this commit https://github.com/ghc/ghc/commit/32f24ddfd9549010dd345733c6f46f67196cacf6

Perhaps it broke at some point? Are you using the x86 backend?