This is xnu-10002.1.13. See this file in:
#include "perf_index.h"
#include "fail.h"
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/sysctl.h>

static char *memblock;
static size_t memsize;

size_t
hw_memsize(void)
{
	int mib[2];
	size_t len;
	size_t my_memsize;
	int retval;

	mib[0] = CTL_HW;
	mib[1] = HW_MEMSIZE;
	len = sizeof(my_memsize);

	retval = sysctl(mib, 2, &my_memsize, &len, NULL, 0);

	if (retval != 0) {
		return 0;
	}

	return my_memsize;
}

DECL_SETUP {
	char *memblockfiller;
	long long i;
	int pgsz = getpagesize();

	/* Heuristic: use half the physical memory, hopefully this should work on all
	 * devices. We use the amount of physical memory, rather than some softer
	 * metric, like amount of free memory, so that the memory allocated is always
	 * consistent for a given device.
	 */
	memsize = hw_memsize();
	VERIFY(memsize > 0, "hw_memsize failed");
	memsize = memsize / 2;

	memblock = (char*)malloc(memsize);
	VERIFY(memblock != NULL, "malloc failed");

	memblockfiller = memblock;

	/* Do this manually, to make sure everything is paged in */
	for (i = 0; i < memsize; i += pgsz) {
		memblockfiller[i] = 1;
	}

	return PERFINDEX_SUCCESS;
}

/* figures out what region of memory to copy, so it does interfere with other
 *  threads,  */
DECL_TEST {
	long long left = length;
	long long region_len = memsize / num_threads / 2;
	long long region_start = memsize / num_threads * thread_id / 2;
	long long copy_len;

	if (thread_id < memsize / 2 % num_threads) {
		region_start += thread_id;
		region_len++;
	} else {
		region_start += memsize / 2 % num_threads;
	}

	while (left > 0) {
		copy_len = region_len < left ? region_len : left;
		memcpy(memblock + region_start + memsize / 2, memblock + region_start, copy_len);
		left -= copy_len;
	}

	return PERFINDEX_SUCCESS;
}

DECL_CLEANUP {
	free(memblock);
	return PERFINDEX_SUCCESS;
}