pcre, bifs, drivers and ports

Ernie Makris <>
Tue Aug 1 15:04:35 CEST 2006


Hi Sean,

Is that one of the drawbacks to a bif implementation? Namely, the bif
call stops the entire emulator? Even with the
SMP version of the emulator?
If this is the case, then I can definitely see why a driver based pcre
should be preferable for a potentially long
running regex computation.

Thanks
Ernie
Sean Hinde wrote:
> Hi Ernie,
>
> On 31 Jul 2006, at 16:21, Ernie Makris wrote:
>
>> Hi Sean
>>
>>>
>>> If you add this feature by hacking the otp release and adding bifs you
>>> would create all the long term issues of having a patched OTP release.
>>>
>> Thats ok, I already patch my releases in order to fix a linux to_erl
>> bug, and to allow the file driver to open /dev/urandom. The only pain is
>> verifying the patch on a new release. But I know the code well enough
>> that I can do it by hand each time.
>
> Where I work we already have a quite heavily patched OTP release so I
> know well the pain. For me the hassle of yet more patches would almost
> certainly outweigh some small speed benefit..
>
>>> You would unlikely to get adopters of any open source version you
>>> released for much the same reason.
>>>
>> I would still put it out there, if anyone wanted to use it, they would
>> be welcome.
>
> And I guess if they liked it enough they could add a driver option :-)
>
>>> OTOH it is not too hard to create a linked in driver that could
>>> alternatively be compiled as a port program. That way you give users a
>>> choice between speed of a driver (almost the same as a BIF), or fault
>>> isolation.
>>>
>> I agree, but I also wanted to see how easy/difficult it would be to add
>> a few new bifs.
>
> One more thing to think on - assuming that pcre itself is thread safe,
> adding it as a driver would make multithreading quite straightforward.
> Mats' comment about limiting length of REs does not really cut it IMO.
> Blocking the whole emulator during a long regexp calculation rarely
> sounds like the right solution for typical Erlang apps.
>
> But. It would be most fascinating to compare real world
> characteristics of:
>
> 1. BIF pcre
> 2. Driver pcre,
> 3. BIF pcre in SMT erlang.
>
> Sean
>
>
>
>



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