Function pmap_advise

freebsd/amd64/amd64/pmap.c:8662–8806

* Apply the given advice to the specified range of addresses within the * given pmap. Depending on the advice, clear the referenced and/or * modified flags in each mapping and set the mapped page's dirty field. */

 *	modified flags in each mapping and set the mapped page's dirty field.
 */
void
pmap_advise(pmap_t pmap, vm_offset_t sva, vm_offset_t eva, int advice)
{
	struct rwlock *lock;
	pml4_entry_t *pml4e;
	pdp_entry_t *pdpe;
	pd_entry_t oldpde, *pde;
	pt_entry_t *pte, PG_A, PG_G, PG_M, PG_RW, PG_V;
	vm_offset_t va, va_next;
	vm_page_t m;
	bool anychanged;

	if (advice != MADV_DONTNEED && advice != MADV_FREE)
		return;

	/*
	 * A/D bit emulation requires an alternate code path when clearing
	 * the modified and accessed bits below. Since this function is
	 * advisory in nature we skip it entirely for pmaps that require
	 * A/D bit emulation.
	 */
	if (pmap_emulate_ad_bits(pmap))
		return;

	PG_A = pmap_accessed_bit(pmap);
	PG_G = pmap_global_bit(pmap);
	PG_M = pmap_modified_bit(pmap);
	PG_V = pmap_valid_bit(pmap);
	PG_RW = pmap_rw_bit(pmap);
	anychanged = false;
	pmap_delayed_invl_start();
	PMAP_LOCK(pmap);
	for (; sva < eva; sva = va_next) {
		pml4e = pmap_pml4e(pmap, sva);
		if (pml4e == NULL || (*pml4e & PG_V) == 0) {
			va_next = (sva + NBPML4) & ~PML4MASK;
			if (va_next < sva)
				va_next = eva;
			continue;
		}

		va_next = (sva + NBPDP) & ~PDPMASK;
		if (va_next < sva)
			va_next = eva;
		pdpe = pmap_pml4e_to_pdpe(pml4e, sva);
		if ((*pdpe & PG_V) == 0)
			continue;
		if ((*pdpe & PG_PS) != 0) {
			KASSERT(va_next <= eva,
			    ("partial update of non-transparent 1G mapping "
			    "pdpe %#lx sva %#lx eva %#lx va_next %#lx",
			    *pdpe, sva, eva, va_next));
			continue;
		}

		va_next = (sva + NBPDR) & ~PDRMASK;
		if (va_next < sva)
			va_next = eva;