Author: alc
Date: Sat Oct 1 19:30:28 2016
New Revision: 306558
URL: https://svnweb.freebsd.org/changeset/base/306558
Log:
MFC r305213,305319,305398
As an optimization to the machine-independent layer, change the machine-
dependent pmap_ts_referenced() so that it updates 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() by the machine-
independent layer.
Replace the number 4 in sparc64's pmap_ts_referenced() by
PMAP_TS_REFERENCED_MAX, like we've done elsewhere, e.g., amd64.
Modified:
stable/11/sys/amd64/amd64/pmap.c
stable/11/sys/arm/arm/pmap-v6.c
stable/11/sys/i386/i386/pmap.c
stable/11/sys/sparc64/sparc64/pmap.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/amd64/amd64/pmap.c
==============================================================================
--- stable/11/sys/amd64/amd64/pmap.c Sat Oct 1 17:57:32 2016
(r306557)
+++ stable/11/sys/amd64/amd64/pmap.c Sat Oct 1 19:30:28 2016
(r306558)
@@ -5831,6 +5831,14 @@ safe_to_clear_referenced(pmap_t pmap, pt
* 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.
@@ -5843,7 +5851,7 @@ pmap_ts_referenced(vm_page_t m)
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;
@@ -5878,9 +5886,19 @@ retry:
}
}
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
@@ -5974,11 +5992,15 @@ small_mappings:
}
}
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);
Modified: stable/11/sys/arm/arm/pmap-v6.c
==============================================================================
--- stable/11/sys/arm/arm/pmap-v6.c Sat Oct 1 17:57:32 2016
(r306557)
+++ stable/11/sys/arm/arm/pmap-v6.c Sat Oct 1 19:30:28 2016
(r306558)
@@ -5178,6 +5178,14 @@ pmap_is_referenced(vm_page_t m)
* 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)
@@ -5186,7 +5194,7 @@ pmap_ts_referenced(vm_page_t m)
pv_entry_t pv, pvf;
pmap_t pmap;
pt1_entry_t *pte1p, opte1;
- pt2_entry_t *pte2p;
+ pt2_entry_t *pte2p, opte2;
vm_paddr_t pa;
int rtval = 0;
@@ -5205,6 +5213,14 @@ pmap_ts_referenced(vm_page_t m)
PMAP_LOCK(pmap);
pte1p = pmap_pte1(pmap, pv->pv_va);
opte1 = pte1_load(pte1p);
+ if (pte1_is_dirty(opte1)) {
+ /*
+ * Although "opte1" is mapping a 1MB page, because
+ * this function is called at a 4KB page granularity,
+ * we only update the 4KB page under test.
+ */
+ vm_page_dirty(m);
+ }
if ((opte1 & PTE1_A) != 0) {
/*
* Since this reference bit is shared by 256 4KB pages,
@@ -5253,7 +5269,10 @@ small_mappings:
("%s: not found a link in page %p's pv list", __func__, m));
pte2p = pmap_pte2_quick(pmap, pv->pv_va);
- if ((pte2_load(pte2p) & PTE2_A) != 0) {
+ opte2 = pte2_load(pte2p);
+ if (pte2_is_dirty(opte2))
+ vm_page_dirty(m);
+ if ((opte2 & PTE2_A) != 0) {
pte2_clear_bit(pte2p, PTE2_A);
pmap_tlb_flush(pmap, pv->pv_va);
rtval++;
Modified: stable/11/sys/i386/i386/pmap.c
==============================================================================
--- stable/11/sys/i386/i386/pmap.c Sat Oct 1 17:57:32 2016
(r306557)
+++ stable/11/sys/i386/i386/pmap.c Sat Oct 1 19:30:28 2016
(r306558)
@@ -4802,6 +4802,14 @@ retry:
* 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)
@@ -4828,6 +4836,14 @@ pmap_ts_referenced(vm_page_t m)
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
@@ -4876,6 +4892,8 @@ small_mappings:
("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);
Modified: stable/11/sys/sparc64/sparc64/pmap.c
==============================================================================
--- stable/11/sys/sparc64/sparc64/pmap.c Sat Oct 1 17:57:32 2016
(r306557)
+++ stable/11/sys/sparc64/sparc64/pmap.c Sat Oct 1 19:30:28 2016
(r306558)
@@ -2106,6 +2106,8 @@ pmap_page_is_mapped(vm_page_t m)
return (rv);
}
+#define PMAP_TS_REFERENCED_MAX 5
+
/*
* Return a count of reference bits for a page, clearing those bits.
* It is not necessary for every reference bit to be cleared, but it
@@ -2115,6 +2117,14 @@ pmap_page_is_mapped(vm_page_t m)
* 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)
@@ -2138,7 +2148,10 @@ pmap_ts_referenced(vm_page_t m)
if ((tp->tte_data & TD_PV) == 0)
continue;
data = atomic_clear_long(&tp->tte_data, TD_REF);
- if ((data & TD_REF) != 0 && ++count > 4)
+ if ((data & TD_W) != 0)
+ vm_page_dirty(m);
+ if ((data & TD_REF) != 0 && ++count >=
+ PMAP_TS_REFERENCED_MAX)
break;
} while ((tp = tpn) != NULL && tp != tpf);
}
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