low-level profiling

[Nicolas Frisby]

I'm not passing any flags related to code generation, I don't think.

$HC -H64m -O -Rghc-timing -package array -H32m -hisuf hi -O1 -rtsopts -c
Main.hs -o Main.o

So that'd just be the native code generator, right?.

$ uname -a
Linux cam-05-unx 3.2.0-35-generic #55-Ubuntu SMP Wed Dec 5 17:42:16 UTC
2012 x86_64 x86_64 x86_64 GNU/Linux

Is there a objdump-ish way to directly look for these .size directives?

Thanks Johan.


On Fri, Feb 15, 2013 at 6:18 PM, Johan Tibell <johan.tibell at gmail.com>wrote:

> On Fri, Feb 15, 2013 at 10:05 AM, Nicolas Frisby <nicolas.frisby at 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 at 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?
>
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