Author: alc
Date: Mon May 31 01:43:02 2010
New Revision: 208665
URL: http://svn.freebsd.org/changeset/base/208665
Log:
Merge portions of r208645 and supporting code from the i386 pmap:
When I pushed down the page queues lock into pmap_is_modified(), I created
an ordering dependence: A pmap operation that clears PG_WRITEABLE and calls
vm_page_dirty() must perform the call first. Otherwise, pmap_is_modified()
could return FALSE without acquiring the page queues lock because the page
is not (currently) writeable, and the caller to pmap_is_modified() might
believe that the page's dirty field is clear because it has not seen the
effect of the vm_page_dirty() call.
When I pushed down the page queues lock into pmap_is_modified(), I
overlooked one place where this ordering dependence is violated:
pmap_enter(). In a rare situation pmap_enter() can be called to replace a
dirty mapping to one page with a mapping to another page. (I say rare
because replacements generally occur as a result of a copy-on-write fault,
and so the old page is not dirty.) This change delays clearing PG_WRITEABLE
until after vm_page_dirty() has been called.
Fixing the ordering dependency also makes it easy to introduce a small
optimization: When pmap_enter() used to replace a mapping to one page with a
mapping to another page, it freed the pv entry for the first mapping and
later called the pv entry allocator for the new mapping. Now, pmap_enter()
attempts to recycle the old pv entry, saving two calls to the pv entry
allocator.
Modified:
head/sys/mips/mips/pmap.c
Modified: head/sys/mips/mips/pmap.c
==============================================================================
--- head/sys/mips/mips/pmap.c Sun May 30 23:05:02 2010 (r208664)
+++ head/sys/mips/mips/pmap.c Mon May 31 01:43:02 2010 (r208665)
@@ -163,6 +163,9 @@ static int pv_entry_count = 0, pv_entry_
static PMAP_INLINE void free_pv_entry(pv_entry_t pv);
static pv_entry_t get_pv_entry(pmap_t locked_pmap);
+static void pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va);
+static pv_entry_t pmap_pvh_remove(struct md_page *pvh, pmap_t pmap,
+ vm_offset_t va);
static __inline void pmap_changebit(vm_page_t m, int bit, boolean_t setem);
static vm_page_t pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va,
@@ -171,9 +174,6 @@ static int pmap_remove_pte(struct pmap *
static void pmap_remove_page(struct pmap *pmap, vm_offset_t va);
static void pmap_remove_entry(struct pmap *pmap, vm_page_t m, vm_offset_t va);
static boolean_t pmap_testbit(vm_page_t m, int bit);
-static void
-pmap_insert_entry(pmap_t pmap, vm_offset_t va, vm_page_t mpte,
- vm_page_t m, boolean_t wired);
static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_page_t mpte,
vm_offset_t va, vm_page_t m);
@@ -1385,15 +1385,15 @@ retry:
* the entry. In either case we free the now unused entry.
*/
-static void
-pmap_remove_entry(struct pmap *pmap, vm_page_t m, vm_offset_t va)
+static pv_entry_t
+pmap_pvh_remove(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
{
pv_entry_t pv;
PMAP_LOCK_ASSERT(pmap, MA_OWNED);
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
- if (m->md.pv_list_count < pmap->pm_stats.resident_count) {
- TAILQ_FOREACH(pv, &m->md.pv_list, pv_list) {
+ if (pvh->pv_list_count < pmap->pm_stats.resident_count) {
+ TAILQ_FOREACH(pv, &pvh->pv_list, pv_list) {
if (pmap == pv->pv_pmap && va == pv->pv_va)
break;
}
@@ -1403,39 +1403,33 @@ pmap_remove_entry(struct pmap *pmap, vm_
break;
}
}
+ if (pv != NULL) {
+ TAILQ_REMOVE(&pvh->pv_list, pv, pv_list);
+ pvh->pv_list_count--;
+ TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
+ }
+ return (pv);
+}
- KASSERT(pv != NULL, ("pmap_remove_entry: pv not found, pa %lx va %lx",
- (u_long)VM_PAGE_TO_PHYS(m), (u_long)va));
- TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
- m->md.pv_list_count--;
- if (TAILQ_FIRST(&m->md.pv_list) == NULL)
- vm_page_flag_clear(m, PG_WRITEABLE);
+static void
+pmap_pvh_free(struct md_page *pvh, pmap_t pmap, vm_offset_t va)
+{
+ pv_entry_t pv;
- TAILQ_REMOVE(&pmap->pm_pvlist, pv, pv_plist);
+ pv = pmap_pvh_remove(pvh, pmap, va);
+ KASSERT(pv != NULL, ("pmap_pvh_free: pv not found, pa %lx va %lx",
+ (u_long)VM_PAGE_TO_PHYS(m), (u_long)va));
free_pv_entry(pv);
}
-/*
- * Create a pv entry for page at pa for
- * (pmap, va).
- */
static void
-pmap_insert_entry(pmap_t pmap, vm_offset_t va, vm_page_t mpte, vm_page_t m,
- boolean_t wired)
+pmap_remove_entry(pmap_t pmap, vm_page_t m, vm_offset_t va)
{
- pv_entry_t pv;
-
- pv = get_pv_entry(pmap);
- pv->pv_va = va;
- pv->pv_pmap = pmap;
- pv->pv_ptem = mpte;
- pv->pv_wired = wired;
- PMAP_LOCK_ASSERT(pmap, MA_OWNED);
mtx_assert(&vm_page_queue_mtx, MA_OWNED);
- TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
- TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
- m->md.pv_list_count++;
+ pmap_pvh_free(&m->md, pmap, va);
+ if (TAILQ_EMPTY(&m->md.pv_list))
+ vm_page_flag_clear(m, PG_WRITEABLE);
}
/*
@@ -1740,6 +1734,7 @@ pmap_enter(pmap_t pmap, vm_offset_t va,
vm_offset_t pa, opa;
register pt_entry_t *pte;
pt_entry_t origpte, newpte;
+ pv_entry_t pv;
vm_page_t mpte, om;
int rw = 0;
@@ -1815,6 +1810,9 @@ pmap_enter(pmap_t pmap, vm_offset_t va,
}
goto validate;
}
+
+ pv = NULL;
+
/*
* Mapping has changed, invalidate old range and fall through to
* handle validating new mapping.
@@ -1825,7 +1823,7 @@ pmap_enter(pmap_t pmap, vm_offset_t va,
if (page_is_managed(opa)) {
om = PHYS_TO_VM_PAGE(opa);
- pmap_remove_entry(pmap, om, va);
+ pv = pmap_pvh_remove(&om->md, pmap, va);
}
if (mpte != NULL) {
mpte->wire_count--;
@@ -1844,8 +1842,18 @@ pmap_enter(pmap_t pmap, vm_offset_t va,
if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0) {
KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva,
("pmap_enter: managed mapping within the clean submap"));
- pmap_insert_entry(pmap, va, mpte, m, wired);
- }
+ if (pv == NULL)
+ pv = get_pv_entry(pmap);
+ pv->pv_va = va;
+ pv->pv_pmap = pmap;
+ pv->pv_ptem = mpte;
+ pv->pv_wired = wired;
+ TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
+ TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
+ m->md.pv_list_count++;
+ } else if (pv != NULL)
+ free_pv_entry(pv);
+
/*
* Increment counters
*/
@@ -1897,6 +1905,9 @@ validate:
if (page_is_managed(opa))
vm_page_dirty(om);
}
+ if (page_is_managed(opa) &&
+ TAILQ_EMPTY(&om->md.pv_list))
+ vm_page_flag_clear(om, PG_WRITEABLE);
} else {
*pte = newpte;
}
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