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?