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Unified Diff: src/spaces.h

Issue 115074: Changed the PageIterator class so that it only returns pages existing... (Closed) Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/
Patch Set: Created 11 years, 7 months ago
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Index: src/spaces.h
===================================================================
--- src/spaces.h (revision 1888)
+++ src/spaces.h (working copy)
@@ -511,11 +511,22 @@
//
// A HeapObjectIterator iterates objects from a given address to the
// top of a space. The given address must be below the current
-// allocation pointer (space top). If the space top changes during
-// iteration (because of allocating new objects), the iterator does
-// not iterate new objects. The caller function must create a new
-// iterator starting from the old top in order to visit these new
-// objects. Heap::Scavenage() is such an example.
+// allocation pointer (space top). There are some caveats.
+//
+// (1) If the space top changes upward during iteration (because of
+// allocating new objects), the iterator does not iterate objects
+// above the original space top. The caller must create a new
+// iterator starting from the old top in order to visit these new
+// objects. Heap::Scavenge() is such an example.
+//
+// (2) If new objects are allocated below the original allocation top
+// (e.g., free-list allocation in paged spaces), the new objects
+// may or may not be iterated depending on their position with
+// respect to the current point of iteration.
+//
+// (3) The space top should not change downward during iteration,
+// otherwise the iterator will return not-necessarily-valid
+// objects.
class HeapObjectIterator: public ObjectIterator {
public:
@@ -559,17 +570,35 @@
// -----------------------------------------------------------------------------
-// A PageIterator iterates pages in a space.
+// A PageIterator iterates the pages in a paged space.
//
// The PageIterator class provides three modes for iterating pages in a space:
-// PAGES_IN_USE iterates pages that are in use by the allocator;
-// PAGES_USED_BY_GC iterates pages that hold relocated objects during a
-// mark-compact collection;
+// PAGES_IN_USE iterates pages containing allocated objects.
+// PAGES_USED_BY_MC iterates pages that hold relocated objects during a
+// mark-compact collection.
// ALL_PAGES iterates all pages in the space.
+//
+// There are some caveats.
+//
+// (1) If the space expands during iteration, new pages will not be
+// returned by the iterator in any mode.
+//
+// (2) If new objects are allocated during iteration, they will appear
+// in pages returned by the iterator. Allocation may cause the
+// allocation pointer or MC allocation pointer in the last page to
+// change between constructing the iterator and iterating the last
+// page.
+//
+// (3) The space should not shrink during iteration, otherwise the
+// iterator will return deallocated pages.
class PageIterator BASE_EMBEDDED {
public:
- enum Mode {PAGES_IN_USE, PAGES_USED_BY_MC, ALL_PAGES};
+ enum Mode {
+ PAGES_IN_USE,
+ PAGES_USED_BY_MC,
+ ALL_PAGES
+ };
Erik Corry 2009/05/07 09:48:07 I liked the old version better. Does the style gu
Kevin Millikin (Chromium) 2009/05/07 10:17:17 Not mandated and we have a mix in the codebase. I
PageIterator(PagedSpace* space, Mode mode);
@@ -577,8 +606,9 @@
inline Page* next();
private:
- Page* cur_page_; // next page to return
- Page* stop_page_; // page where to stop
+ PagedSpace* space_;
+ Page* prev_page_; // Previous page returned.
+ Page* stop_page_; // Page to stop at (last page returned by the iterator).
};
@@ -809,6 +839,9 @@
// The first page in this space.
Page* first_page_;
+ // The last page in this space.
+ Page* last_page_;
Erik Corry 2009/05/07 09:48:07 The way this is updated is subtle. It at least de
Kevin Millikin (Chromium) 2009/05/07 10:17:17 Commented here and in the places where it's modifi
+
// Normal allocation information.
AllocationInfo allocation_info_;
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