[erlang-questions] Performance question

[Stu Bailey]

I'm not planning to spend a lot of time on this right now, but the
binary:replace(...) was chewing a tremendous amount of system time CPU load
(and actually never finished before I got frustrated and killed it) and my
function was reporting the CPU load as 99% user time (not system time) and
finished in a reasonable time.   I assume the high system time usage for
binary:replace(..)  is because binary:replace(...) is doing something manic
with system calls for memory management or something?


On Fri, Nov 7, 2014 at 1:44 AM, Loïc Hoguin <essen@REDACTED> wrote:

> binary:split and binary:replace, unlike other functions of the binary
> module, are normal Erlang functions. They also process a list of options
> before doing the actual work, so there's an obvious overhead compared to
> not doing that. In addition as has been pointed out, your code is more
> specialized so that helps too.
>
> On 11/07/2014 03:33 AM, Stu Bailey wrote:
>
>> I found
>>
>> binary:replace(BinChunk,<<"\n">>,<<>>,[global]).
>>
>> /significantly /slower than
>>
>> remove_pattern(BinChunk,<<>>,<<"\n">>).
>>
>> with
>>
>> remove_pattern(<<>>,Acc,_BinPat) ->
>>      Acc;
>> remove_pattern(Bin,Acc,BinPat)->
>>      <<Byte:1/binary,Rest/binary>> = Bin,
>>      case Byte == BinPat of
>> true -> remove_pattern(Rest,Acc,BinPat);
>> false -> remove_pattern(Rest,<<Acc/binary,Byte/binary>>,BinPat)
>>      end.
>>
>> That was surprising to me.  The built-in binary:replace() was much much
>> slower for larger BinChunk with lots of <<"\n">> sprinkled through.
>>
>> Thoughts?
>>
>>
>> _______________________________________________
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>>
>>
> --
> Loïc Hoguin
> http://ninenines.eu
>
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