Does 
void do_simulation() {
    struct s* m;
    m = (struct s*)malloc(10000000 * sizeof(struct s));
    free(m);
    m = (struct s*)malloc(10000000 * sizeof(struct s));
    free(m);
}

[download]
use more memory than 
void do_simulation() {
    struct s* m = (struct s*)malloc(10000000 * sizeof(struct s));
    free(m);
}

[download]

It could be that the memory is being pout back into Perl's free memory pool and you just don't realize it.

In reply to Re: Calling a C function using malloc() in a XS by ikegami
in thread Calling a C function using malloc() in a XS by Anonymous Monk

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