RE: [Boost-users] Changing the heap allocator

13 Apr 2004

      ...
-----Original Message-----
From: boost-users-bounces@lists.boost.org [mailto:boost-users-
bounces@lists.boost.org] On Behalf Of Victor A. Wagner Jr.
Sent: Saturday, 10 April 2004 4:16 PM
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] Changing the heap allocator
re: (because of msvcp60.dll)
that may sum up the entire problem.... VC++6.0 is
broken...period...simple
statement of fact
it was replaced 2 years ago by .net then again by .net2003
you may wish to test with a current version
...
Hi,
I'm working on a project where I've replaced Microsoft's (terrible)
heap
allocator with the Doug Lea allocator.  There seems to be some cases
where
the Windows XP allocator is 500 times slower than it should be.  This
made
my program take minutes rather than seconds to run.  To try to
understand
what kind of allocation patterns cause the behaviour I wrote a small
console application (see below).  After playing around with different
allocation patterns for half an hour I found a case where the
At Wednesday 2004-04-07 19:54, you wrote:
pathological
...
behaviour appeared.  I'm none the wiser about the problem.  For
example,
moving the malloc(301) statement before the 7 x malloc(1000) makes
...
...
problem go away!   However, given the ease with which I rediscovered
Hi Victor,

The CRT library that comes with VC is only a thin wrapper for the heap
allocator implemented in kernel.dll - see HeapAlloc() in MSDN.   For
that reason it won't make any difference what version of VC is used.

Note that I haven't seen the pathological behavior with Windows 98.

Does anyone know how to enable the LFH (low fragmentation heap) for the
heap created by the VC CRT?

- David

the
the
...
...
problem, I wonder why there aren't more complaints about Microsoft's
heap
allocator.  With some allocation patterns I have seen the allocator
fall
below 1kHz on a Pentium IV 2GHz machine!
I've created a library that exports alternative versions of operator
new
and operator delete, by using a def file as follows
EXPORTS
      ??2@YAPAXI@Z
      ??3@YAXPAX@Z
I've had to do some hacky things to make it work with the STL
(because of
msvcp60.dll) , but that's another story!
Now my question : I want to use boost, but need to work out how to
make
it
use a different allocator.  Will I need to rebuild the boost dlls
(such
as
boost_python.dll),  against my static library?
Regards,
David Barrett-Lennard
/////////////////////// heap allocation test
///////////////////////////
#include <iostream>
#include <time.h>
int main(int argc, char* argv[])
{
    for (int count=1 ; count <= 5 ; ++count)
    {
        int n1 = 0, n2 = 0;
        clock_t start = clock();
        {
            const int NUM = 10000;
            void* L[NUM*7];
            for (int i=0 ; i < NUM ; ++i)
            {
                for (int j=0 ; j < 7 ; ++j) L[n1++] = malloc(1000);
                void* leak = malloc(301);
                ++n2;
            }
            for (int k=n1-1 ; k >= 0 ; --k) free(L[k]);
        }
        clock_t elapsed = clock()-start;
        if (elapsed)
        {
            std::cout << "Time = " << elapsed << " ms"
                      << "  Rate = " << 1000 * (n1 + n2) / elapsed
<< "
Hz"
                      << std::endl;
        }
    }
    return 0;
}
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Victor A. Wagner Jr.      http://rudbek.com
The five most dangerous words in the English language:
               "There oughta be a law"
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