/**
* Allocation of a physical page.
*
* 1. First, implement a naive page allocator that scans the allocation table (AT)
* using the functions defined in import.h to find the first unallocated page
* with usable permission.
* (Q: Do you have to scan allocation table from index 0? Recall how you have
* initialized the table in pmem_init.)
* Then mark the page as allocated in the allocation table and return the page
* index of the page found. In the case when there is no avaiable page found,
* return 0.
* 2. Optimize the code with the memorization techniques so that you do not have to
* scan the allocation table from scratch every time.
*/
unsigned int
palloc()
{
unsigned int tnps;
unsigned int palloc_index;
unsigned int palloc_cur_at;
unsigned int palloc_is_norm;
unsigned int palloc_free_index;
tnps = get_nps();
palloc_index = last_palloc_index + 1;
palloc_free_index = tnps;
while( palloc_index < tnps && palloc_free_index == tnps )
{
palloc_is_norm = at_is_norm(palloc_index);
if (palloc_is_norm == 1)
{
palloc_cur_at = at_is_allocated(palloc_index);
if (palloc_cur_at == 0)
palloc_free_index = palloc_index;
}
palloc_index ++;
}
if (palloc_free_index == tnps)
palloc_free_index = 0;
else
{
at_set_allocated(palloc_free_index, 1);
}
last_palloc_index = palloc_free_index % tnps;
return palloc_free_index;
}
int MATIntro_test3()
{
at_set_allocated(1, 0);
if (at_is_allocated(1) != 0) {
at_set_allocated(1, 0);
dprintf("test 3 failed.\n");
return 1;
}
at_set_allocated(1, 1);
if (at_is_allocated(1) != 1) {
at_set_allocated(1, 0);
dprintf("test 3 failed.\n");
return 1;
}
at_set_allocated(1, 100);
if (at_is_allocated(1) != 1) {
at_set_allocated(1, 0);
dprintf("test 3 failed.\n");
return 1;
}
at_set_allocated(1, 0);
dprintf("test 3 passed.\n");
return 0;
}
/**
* Free of a physical page.
*
* This function marks the page with given index as unallocated
* in the allocation table.
*
* Hint: Simple.
*/
void
pfree(unsigned int pfree_index)
{
at_set_allocated(pfree_index, 0);
}
