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From Martin Sebor <>
Subject Re: stdcxx 4.2.0/4.1.3 binary incompatibility on Linux
Date Wed, 17 Oct 2007 20:06:37 GMT
Mark Brown wrote:
> On 10/17/07, Martin Sebor <> wrote:
>> Okay, I've got it:
>> Damn that was hard!
>> So, what do we do? Going back to using a mutex for strings would
>> be *huge* performance hit on one of the most popular platforms
>> (if not the most popular one), but then again, keeping the status
>> quo will break binary compatibility on the (now) most popular
>> platform.
>> Opinions?
> Maybe it isn't as bad as you think. Have you done any measurements of
> the performance difference between the previous version and 4.2.0?

It is quite bad. Here are timings for 4 threads (running on
a 4 CPU dual core Xeon) copying the same global string object
5 million times:

                4.1.x        4.2.0
     real    0m38.464s    0m 8.660s
     user    0m26.685s    0m33.655s
     sys     1m54.129s    0m 0.001s

I was hoping that stdcxx 4.1.2 wouldn't build on x86_64 and
that the platform would be new for 4.1.3 (and could thought
of as experimental, giving us a possible excuse to break
compatibility) but no such luck. It builds fine and has the
mutex in it, just like 4.1.3.


> -- Mark

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