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Index: head/sys/amd64/amd64/pmap.c
===================================================================
--- head/sys/amd64/amd64/pmap.c
+++ head/sys/amd64/amd64/pmap.c
@@ -5843,6 +5843,14 @@
* should be tested and standardized at some point in the future for
* optimal aging of shared pages.
*
+ * As an optimization, update the page's dirty field if a modified bit is
+ * found while counting reference bits. This opportunistic update can be
+ * performed at low cost and can eliminate the need for some future calls
+ * to pmap_is_modified(). However, since this function stops after
+ * finding PMAP_TS_REFERENCED_MAX reference bits, it may not detect some
+ * dirty pages. Those dirty pages will only be detected by a future call
+ * to pmap_is_modified().
+ *
* A DI block is not needed within this function, because
* invalidations are performed before the PV list lock is
* released.
@@ -5855,7 +5863,7 @@
pmap_t pmap;
struct rwlock *lock;
pd_entry_t oldpde, *pde;
- pt_entry_t *pte, PG_A;
+ pt_entry_t *pte, PG_A, PG_M, PG_RW;
vm_offset_t va;
vm_paddr_t pa;
int cleared, md_gen, not_cleared, pvh_gen;
@@ -5890,9 +5898,19 @@
}
}
PG_A = pmap_accessed_bit(pmap);
+ PG_M = pmap_modified_bit(pmap);
+ PG_RW = pmap_rw_bit(pmap);
va = pv->pv_va;
pde = pmap_pde(pmap, pv->pv_va);
oldpde = *pde;
+ if ((oldpde & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
+ /*
+ * Although "oldpde" is mapping a 2MB page, because
+ * this function is called at a 4KB page granularity,
+ * we only update the 4KB page under test.
+ */
+ vm_page_dirty(m);
+ }
if ((*pde & PG_A) != 0) {
/*
* Since this reference bit is shared by 512 4KB
@@ -5986,11 +6004,15 @@
}
}
PG_A = pmap_accessed_bit(pmap);
+ PG_M = pmap_modified_bit(pmap);
+ PG_RW = pmap_rw_bit(pmap);
pde = pmap_pde(pmap, pv->pv_va);
KASSERT((*pde & PG_PS) == 0,
("pmap_ts_referenced: found a 2mpage in page %p's pv list",
m));
pte = pmap_pde_to_pte(pde, pv->pv_va);
+ if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW))
+ vm_page_dirty(m);
if ((*pte & PG_A) != 0) {
if (safe_to_clear_referenced(pmap, *pte)) {
atomic_clear_long(pte, PG_A);
Index: head/sys/i386/i386/pmap.c
===================================================================
--- head/sys/i386/i386/pmap.c
+++ head/sys/i386/i386/pmap.c
@@ -4798,6 +4798,14 @@
* XXX: The exact number of bits to check and clear is a matter that
* should be tested and standardized at some point in the future for
* optimal aging of shared pages.
+ *
+ * As an optimization, update the page's dirty field if a modified bit is
+ * found while counting reference bits. This opportunistic update can be
+ * performed at low cost and can eliminate the need for some future calls
+ * to pmap_is_modified(). However, since this function stops after
+ * finding PMAP_TS_REFERENCED_MAX reference bits, it may not detect some
+ * dirty pages. Those dirty pages will only be detected by a future call
+ * to pmap_is_modified().
*/
int
pmap_ts_referenced(vm_page_t m)
@@ -4824,6 +4832,14 @@
pmap = PV_PMAP(pv);
PMAP_LOCK(pmap);
pde = pmap_pde(pmap, pv->pv_va);
+ if ((*pde & (PG_M | PG_RW)) == (PG_M | PG_RW)) {
+ /*
+ * Although "*pde" is mapping a 2/4MB page, because
+ * this function is called at a 4KB page granularity,
+ * we only update the 4KB page under test.
+ */
+ vm_page_dirty(m);
+ }
if ((*pde & PG_A) != 0) {
/*
* Since this reference bit is shared by either 1024
@@ -4872,6 +4888,8 @@
("pmap_ts_referenced: found a 4mpage in page %p's pv list",
m));
pte = pmap_pte_quick(pmap, pv->pv_va);
+ if ((*pte & (PG_M | PG_RW)) == (PG_M | PG_RW))
+ vm_page_dirty(m);
if ((*pte & PG_A) != 0) {
atomic_clear_int((u_int *)pte, PG_A);
pmap_invalidate_page(pmap, pv->pv_va);

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