kernel/vm: Move committed_size to the cache implementations.

This fixes a long-standing TODO, and a major inconsistency
that for different caches, "commitment" reserves from different
pools, so any two aren't necessarily convertible.

The new system introduces a virtual method "TakeCommitmentFrom",
which allows the VM's cut_area routine to behave as it did
previously.

headers/private/kernel/vm/VMCache.h

@@ -147,9 +147,10 @@ public:
 
 			status_t			SetMinimalCommitment(off_t commitment,
 									int priority);
-			off_t				Commitment() const;
+	virtual	off_t				Commitment() const;
 	virtual	bool				CanOvercommit();
 	virtual	status_t			Commit(off_t size, int priority);
+	virtual	void				TakeCommitmentFrom(VMCache* from, off_t commitment);
 
 	// backing store operations
 	virtual	bool				StoreHasPage(off_t offset);
@@ -206,8 +207,6 @@ public:
 			VMCache*			source;
 			off_t				virtual_base;
 			off_t				virtual_end;
-			off_t				committed_size;
-				// TODO: Remove!
 			uint32				page_count;
 			uint32				temporary : 1;
 			uint32				type : 6;

src/system/kernel/vm/VMAnonymousCache.cpp

@@ -452,7 +452,7 @@ VMAnonymousCache::~VMAnonymousCache()
 
 	_FreeSwapPageRange(virtual_base, virtual_end, false);
 	swap_space_unreserve(fReservedSwapSize);
-	vm_unreserve_memory_or_swap(committed_size);
+	vm_unreserve_memory_or_swap(fCommittedSize);
 }
 
 
@@ -469,6 +469,7 @@ VMAnonymousCache::Init(bool canOvercommit, int32 numPrecommittedPages,
 	if (error != B_OK)
 		return error;
 
+	fCommittedSize = 0;
 	fCanOvercommit = canOvercommit;
 	fHasPrecommitted = false;
 	fPrecommittedPages = min_c(numPrecommittedPages, 255);
@@ -612,7 +613,7 @@ VMAnonymousCache::Discard(off_t offset, off_t size)
 	_FreeSwapPageRange(offset, offset + size);
 	const ssize_t discarded = VMCache::Discard(offset, size);
 	if (discarded > 0 && fCanOvercommit)
-		Commit(committed_size - discarded, VM_PRIORITY_USER);
+		Commit(fCommittedSize - discarded, VM_PRIORITY_USER);
 	return discarded;
 }
 
@@ -724,14 +725,28 @@ VMAnonymousCache::Adopt(VMCache* _source, off_t offset, off_t size,
 		// We need to adopt the commitment for these pages.
 		uint32 newPages = page_count - initialPageCount;
 		off_t pagesCommitment = newPages * B_PAGE_SIZE;
-		source->committed_size -= pagesCommitment;
+		source->fCommittedSize -= pagesCommitment;
-		committed_size += pagesCommitment;
+		fCommittedSize += pagesCommitment;
 	}
 
 	return status;
 }
 
 
+off_t
+VMAnonymousCache::Commitment() const
+{
+	return fCommittedSize;
+}
+
+
+bool
+VMAnonymousCache::CanOvercommit()
+{
+	return fCanOvercommit;
+}
+
+
 status_t
 VMAnonymousCache::Commit(off_t size, int priority)
 {
@@ -743,7 +758,7 @@ VMAnonymousCache::Commit(off_t size, int priority)
 
 	// If we can overcommit, we don't commit here, but in Fault(). We always
 	// unreserve memory, if we're asked to shrink our commitment, though.
-	if (fCanOvercommit && size > committed_size) {
+	if (fCanOvercommit && size > fCommittedSize) {
 		if (fHasPrecommitted)
 			return B_OK;
 
@@ -754,31 +769,37 @@ VMAnonymousCache::Commit(off_t size, int priority)
 			size = precommitted;
 
 		// pre-commit should not shrink existing commitment
-		size += committed_size;
+		size += fCommittedSize;
 	}
 
 	// Check to see how much we could commit - we need real memory
 
-	if (size > committed_size) {
+	if (size > fCommittedSize) {
 		// try to commit
-		if (vm_try_reserve_memory_or_swap(size - committed_size, priority, 1000000)
+		if (vm_try_reserve_memory_or_swap(size - fCommittedSize, priority, 1000000)
 				!= B_OK) {
 			return B_NO_MEMORY;
 		}
 	} else {
 		// we can release some
-		vm_unreserve_memory_or_swap(committed_size - size);
+		vm_unreserve_memory_or_swap(fCommittedSize - size);
 	}
 
-	committed_size = size;
+	fCommittedSize = size;
 	return B_OK;
 }
 
 
-bool
+void
-VMAnonymousCache::CanOvercommit()
+VMAnonymousCache::TakeCommitmentFrom(VMCache* _from, off_t commitment)
 {
-	return fCanOvercommit;
+	VMAnonymousCache* from = dynamic_cast<VMAnonymousCache*>(_from);
+	ASSERT(from != NULL && from->fCommittedSize >= commitment);
+	AssertLocked();
+	from->AssertLocked();
+
+	from->fCommittedSize -= commitment;
+	fCommittedSize += commitment;
 }
 
 
@@ -1046,7 +1067,7 @@ VMAnonymousCache::Fault(struct VMAddressSpace* aspace, off_t offset)
 	if (fCanOvercommit && LookupPage(offset) == NULL && !StoreHasPage(offset)) {
 		if (fPrecommittedPages == 0) {
 			// never commit more than needed
-			if (committed_size / B_PAGE_SIZE > page_count)
+			if (fCommittedSize / B_PAGE_SIZE > page_count)
 				return B_BAD_HANDLER;
 
 			// try to commit additional memory
@@ -1058,7 +1079,7 @@ VMAnonymousCache::Fault(struct VMAddressSpace* aspace, off_t offset)
 				return B_NO_MEMORY;
 			}
 
-			committed_size += B_PAGE_SIZE;
+			fCommittedSize += B_PAGE_SIZE;
 		} else
 			fPrecommittedPages--;
 	}
@@ -1079,13 +1100,13 @@ VMAnonymousCache::Merge(VMCache* _source)
 	}
 
 	// take over the source's committed size
-	committed_size += source->committed_size;
+	fCommittedSize += source->fCommittedSize;
-	source->committed_size = 0;
+	source->fCommittedSize = 0;
 
 	off_t actualSize = PAGE_ALIGN(virtual_end - virtual_base);
-	if (committed_size > actualSize) {
+	if (fCommittedSize > actualSize) {
-		vm_unreserve_memory_or_swap(committed_size - actualSize);
+		vm_unreserve_memory_or_swap(fCommittedSize - actualSize);
-		committed_size = actualSize;
+		fCommittedSize = actualSize;
 	}
 
 	// Move all not shadowed swap pages from the source to the consumer cache.

src/system/kernel/vm/VMAnonymousCache.h

@@ -48,8 +48,11 @@ public:
 
 	virtual	ssize_t				Discard(off_t offset, off_t size);
 
+	virtual	off_t				Commitment() const;
 	virtual	bool				CanOvercommit();
 	virtual	status_t			Commit(off_t size, int priority);
+	virtual	void				TakeCommitmentFrom(VMCache* from, off_t commitment);
+
 	virtual	bool				StoreHasPage(off_t offset);
 	virtual	bool				DebugStoreHasPage(off_t offset);
 
@@ -100,6 +103,7 @@ private:
 private:
 	friend bool swap_free_page_swap_space(vm_page* page);
 
+			off_t				fCommittedSize;
 			bool				fCanOvercommit;
 			bool				fHasPrecommitted;
 			uint8				fPrecommittedPages;

src/system/kernel/vm/VMAnonymousNoSwapCache.cpp

@@ -49,6 +49,7 @@ VMAnonymousNoSwapCache::Init(bool canOvercommit, int32 numPrecommittedPages,
 	if (error != B_OK)
 		return error;
 
+	committed_size = 0;
 	fCanOvercommit = canOvercommit;
 	fHasPrecommitted = false;
 	fPrecommittedPages = min_c(numPrecommittedPages, 255);
@@ -59,14 +60,19 @@ VMAnonymousNoSwapCache::Init(bool canOvercommit, int32 numPrecommittedPages,
 
 
 status_t
-VMAnonymousNoSwapCache::Adopt(VMCache* from, off_t offset, off_t size,
+VMAnonymousNoSwapCache::Adopt(VMCache* _from, off_t offset, off_t size,
 	off_t newOffset)
 {
+	VMAnonymousNoSwapCache* from = dynamic_cast<VMAnonymousNoSwapCache*>(_from);
+	ASSERT(from != NULL);
+
 	uint32 initialPageCount = page_count;
 	status_t status = VMCache::Adopt(from, offset, size, newOffset);
 
 	if (fCanOvercommit) {
 		// We need to adopt the commitment for these pages.
+		ASSERT(from->fCanOvercommit);
+
 		uint32 newPages = page_count - initialPageCount;
 		off_t pagesCommitment = newPages * B_PAGE_SIZE;
 		from->committed_size -= pagesCommitment;
@@ -87,6 +93,20 @@ VMAnonymousNoSwapCache::Discard(off_t offset, off_t size)
 }
 
 
+off_t
+VMAnonymousNoSwapCache::Commitment() const
+{
+	return committed_size;
+}
+
+
+bool
+VMAnonymousNoSwapCache::CanOvercommit()
+{
+	return fCanOvercommit;
+}
+
+
 status_t
 VMAnonymousNoSwapCache::Commit(off_t size, int priority)
 {
@@ -127,10 +147,16 @@ VMAnonymousNoSwapCache::Commit(off_t size, int priority)
 }
 
 
-bool
+void
-VMAnonymousNoSwapCache::CanOvercommit()
+VMAnonymousNoSwapCache::TakeCommitmentFrom(VMCache* _from, off_t commitment)
 {
-	return fCanOvercommit;
+	VMAnonymousNoSwapCache* from = dynamic_cast<VMAnonymousNoSwapCache*>(_from);
+	ASSERT(from != NULL && from->committed_size >= commitment);
+	AssertLocked();
+	from->AssertLocked();
+
+	from->committed_size -= commitment;
+	committed_size += commitment;
 }
 
 

src/system/kernel/vm/VMAnonymousNoSwapCache.h

@@ -26,8 +26,11 @@ public:
 									off_t newOffset);
 	virtual	ssize_t				Discard(off_t offset, off_t size);
 
+	virtual	off_t				Commitment() const;
 	virtual	bool				CanOvercommit();
 	virtual	status_t			Commit(off_t size, int priority);
+	virtual	void				TakeCommitmentFrom(VMCache* from, off_t commitment);
+
 	virtual	bool				StoreHasPage(off_t offset);
 
 	virtual	int32				GuardSize()	{ return fGuardedSize; }
@@ -49,6 +52,9 @@ public:
 protected:
 	virtual	void				DeleteObject();
 
+public:
+			off_t				committed_size;
+
 private:
 			bool				fCanOvercommit;
 			bool				fHasPrecommitted;

src/system/kernel/vm/VMCache.cpp

@@ -638,7 +638,6 @@ VMCache::Init(const char* name, uint32 cacheType, uint32 allocationFlags)
 	source = NULL;
 	virtual_base = 0;
 	virtual_end = 0;
-	committed_size = 0;
 	temporary = 0;
 	page_count = 0;
 	fWiredPagesCount = 0;
@@ -1310,7 +1309,7 @@ VMCache::FlushAndRemoveAllPages()
 off_t
 VMCache::Commitment() const
 {
-	return committed_size;
+	return 0;
 }
 
 
@@ -1329,6 +1328,13 @@ VMCache::Commit(off_t size, int priority)
 }
 
 
+void
+VMCache::TakeCommitmentFrom(VMCache* from, off_t commitment)
+{
+	ASSERT_UNREACHABLE();
+}
+
+
 /*!	Returns whether the cache's underlying backing store could deliver the
 	page at the given offset.
 

src/system/kernel/vm/vm.cpp

@@ -969,9 +969,8 @@ cut_area(VMAddressSpace* addressSpace, VMArea* area, addr_t address,
 		if (!overcommitting && resizePriority != -1) {
 			// Steal some of the original cache's commitment.
 			const size_t steal = PAGE_ALIGN(secondSize);
-			if (cache->committed_size > (off_t)steal) {
+			if (cache->Commitment() > (off_t)steal) {
-				cache->committed_size -= steal;
+				secondCache->TakeCommitmentFrom(cache, steal);
-				secondCache->committed_size += steal;
 				commitmentStolen = steal;
 			}
 		}
@@ -1001,8 +1000,7 @@ cut_area(VMAddressSpace* addressSpace, VMArea* area, addr_t address,
 		}
 
 		if (error != B_OK) {
-			secondCache->committed_size -= commitmentStolen;
+			cache->TakeCommitmentFrom(secondCache, commitmentStolen);
-			cache->committed_size += commitmentStolen;
 
 			// Move the pages back.
 			status_t readoptStatus = cache->Adopt(secondCache,
@@ -1036,9 +1034,9 @@ cut_area(VMAddressSpace* addressSpace, VMArea* area, addr_t address,
 		if (resizePriority == -1) {
 			// Adjust commitments.
 			const off_t areaCommit = compute_area_page_commitment(area) * B_PAGE_SIZE;
-			if (areaCommit < area->cache->committed_size) {
+			if (areaCommit < area->cache->Commitment()) {
-				secondArea->cache->committed_size += area->cache->committed_size - areaCommit;
+				secondArea->cache->TakeCommitmentFrom(area->cache,
-				area->cache->committed_size = areaCommit;
+					area->cache->Commitment() - areaCommit);
 			}
 			area->cache->Commit(areaCommit, priority);
 
@@ -1768,9 +1766,12 @@ vm_create_anonymous_area(team_id team, const char *name, addr_t size,
 
 	cache->temporary = 1;
 	cache->virtual_end = size;
-	cache->committed_size = reservedMemory;
+
-		// TODO: This should be done via a method.
+	if (reservedMemory != 0) {
-	reservedMemory = 0;
+		VMAnonymousNoSwapCache* noSwapCache = dynamic_cast<VMAnonymousNoSwapCache*>(cache);
+		noSwapCache->committed_size = reservedMemory;
+		reservedMemory = 0;
+	}
 
 	cache->Lock();
 
@@ -2864,16 +2865,15 @@ vm_copy_on_write_area(VMCache* lowerCache,
 
 	// Shrink the lower cache's commitment (if possible) and steal the remainder;
 	// and increase the upper cache's commitment to the lower cache's old commitment.
-	const off_t lowerOldCommitment = lowerCache->committed_size,
+	const off_t lowerOldCommitment = lowerCache->Commitment(),
 		lowerNewCommitment = (lowerCache->page_count * B_PAGE_SIZE);
 	if (lowerNewCommitment < lowerOldCommitment) {
-		lowerCache->committed_size = lowerNewCommitment;
+		upperCache->TakeCommitmentFrom(lowerCache,
-		upperCache->committed_size = lowerOldCommitment - lowerNewCommitment;
+			lowerOldCommitment - lowerNewCommitment);
 	}
 	status = upperCache->Commit(lowerOldCommitment, VM_PRIORITY_USER);
 	if (status != B_OK) {
-		lowerCache->committed_size += upperCache->committed_size;
+		lowerCache->TakeCommitmentFrom(upperCache, upperCache->Commitment());
-		upperCache->committed_size = 0;
 		upperCache->ReleaseRefAndUnlock();
 		return status;
 	}