Re: malloc_zone_batch_malloc

22 May 2008

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Thanks.

It seems odd.  I tried another machine, and like your
experience, it works.

This is what I see on the two machines:

i386-darwin-cereal % uname -a
Darwin cereal .totalviewtech.com 8.4.1 Darwin Kernel Version 8.4.1: Tue Jan  3 18:23:53 PST 2006; root:xnu-792.7.90.obj~1/RELEASE_I386 i386 i386

386-darwin-cereal% ./t_mailing_list_repro
do_experiment to size 16777216 returned 0

i386-darwin-wheat% uname -a
Darwin wheat.totalviewtech.com 9.0.0 Darwin Kernel Version 9.0.0: Tue Oct  9 21:35:55 PDT 2007; root:xnu-1228~1/RELEASE_I386 i386

386-darwin-wheat% ./t_mailing_list_repro
do_experiment to size 16777216 returned 1

What, I wonder, has changed?

Ariel
==

On Wed 21 May 17:35, Eric Gouriou wrote:
...
On May 21, 2008, at 5:03 PM, Ariel Burton wrote:
...
The test program I included in my original
psoting, however, tries all sizes from 1 bytes
to 16mb without coming across a case where the
routine returns a non-zero value.
Am I missing something?
Works for me on Leopard 10.5.2 .
------
// cc -Wall --std=c99 -o mzm mzm.c
#include  <stdio.h>
#include  <malloc/malloc.h>
static size_t
do_experiment (malloc_zone_t *z, size_t size_bound)
{
 size_t  ret_val = 0;
 void    *v[ 2 ];
for (size_t size = 1; size < size_bound; size++)
 {
     unsigned allocated = malloc_zone_batch_malloc ( z, size, v, 2 );
     if (allocated) {
       ret_val = size;
       break;
     }
 }
return ret_val;
} /* do_experiment */
int
main (int argc, const char *argv [])
{
 size_t          size_bound = 16 * 1024 * 1024;
 malloc_zone_t  *z = malloc_default_zone();
size_t size = do_experiment(z, size_bound);
printf("do_experiment to size %zd returned %zd\n", size_bound, size);
return 0;
}
-------
% cc -Wall --std=c99 -o mzm mzm.c
% ./mzm
do_experiment to size 16777216 returned 1
-------
Of course I may have failed reading comprehension 201 this time
around...
Eric
...
Ariel Burton
==
On Wed 21 May 16:37, Terry Lambert wrote:
...
On May 21, 2008, at 2:00 PM, Ariel Burton wrote:
...
In what circumstances is malloc_zone_batch_malloc
supposed to return any memory?
<http://developer.apple.com/documentation/Performance/Conceptual/ManagingMemo...
...
"f your code allocates multiple, identically-sized memory blocks, you
can use the malloc_zone_batch_malloc function to allocate those
blocks
all at once. This function offers better performance than the
equivalent series of calls to malloc to allocate the same memory.
Performance is best when the individual block size is relatively
small—
less than 4K in size. The function does its best to allocate all of
the requested memory but may return less than was requested. When
using this function, check the return values carefully to see how
many
blocks were actually allocated."
-- Terry
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Ariel Burton

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