Mercurial > hg > truffle
diff src/share/vm/gc_implementation/shared/spaceDecorator.hpp @ 263:12eea04c8b06
6672698: mangle_unused_area() should not remangle the entire heap at each collection.
Summary: Maintain a high water mark for the allocations in a space and mangle only up to that high water mark.
Reviewed-by: ysr, apetrusenko
author | jmasa |
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date | Wed, 09 Jul 2008 15:08:55 -0700 |
parents | |
children | 9ee9cf798b59 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/shared/spaceDecorator.hpp Wed Jul 09 15:08:55 2008 -0700 @@ -0,0 +1,141 @@ +/* + * Copyright 2002-2005 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +class SpaceDecorator: public AllStatic { + public: + // Initialization flags. + static const bool Clear = true; + static const bool DontClear = false; + static const bool Mangle = true; + static const bool DontMangle = false; +}; + +// Functionality for use with class Space and class MutableSpace. +// The approach taken with the mangling is to mangle all +// the space initially and then to mangle areas that have +// been allocated since the last collection. Mangling is +// done in the context of a generation and in the context +// of a space. +// The space in a generation is mangled when it is first +// initialized and when the generation grows. The spaces +// are not necessarily up-to-date when this mangling occurs +// and the method mangle_region() is used. +// After allocations have been done in a space, the space generally +// need to be remangled. Remangling is only done on the +// recently allocated regions in the space. Typically, that is +// the region between the new top and the top just before a +// garbage collection. +// An exception to the usual mangling in a space is done when the +// space is used for an extraordinary purpose. Specifically, when +// to-space is used as scratch space for a mark-sweep-compact +// collection. +// Spaces are mangled after a collection. If the generation +// grows after a collection, the added space is mangled as part of +// the growth of the generation. No additional mangling is needed when the +// spaces are resized after an expansion. +// The class SpaceMangler keeps a pointer to the top of the allocated +// area and provides the methods for doing the piece meal mangling. +// Methods for doing sparces and full checking of the mangling are +// included. The full checking is done if DEBUG_MANGLING is defined. +// GenSpaceMangler is used with the GenCollectedHeap collectors and +// MutableSpaceMangler is used with the ParallelScavengeHeap collectors. +// These subclasses abstract the differences in the types of spaces used +// by each heap. + +class SpaceMangler: public CHeapObj { + friend class VMStructs; + + // High water mark for allocations. Typically, the space above + // this point have been mangle previously and don't need to be + // touched again. Space belows this point has been allocated + // and remangling is needed between the current top and this + // high water mark. + HeapWord* _top_for_allocations; + HeapWord* top_for_allocations() { return _top_for_allocations; } + + public: + + // Setting _top_for_allocations to NULL at initialization + // makes it always below top so that mangling done as part + // of the initialize() call of a space does nothing (as it + // should since the mangling is done as part of the constructor + // for the space. + SpaceMangler() : _top_for_allocations(NULL) {} + + // Methods for top and end that delegate to the specific + // space type. + virtual HeapWord* top() const = 0; + virtual HeapWord* end() const = 0; + + // Return true if q matches the mangled pattern. + static bool is_mangled(HeapWord* q) PRODUCT_RETURN0; + + // Used to save the an address in a space for later use during mangling. + void set_top_for_allocations(HeapWord* v); + + // Overwrites the unused portion of this space. + // Mangle only the region not previously mangled [top, top_previously_mangled) + void mangle_unused_area(); + // Mangle all the unused region [top, end) + void mangle_unused_area_complete(); + // Do some sparse checking on the area that should have been mangled. + void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN; + // Do a complete check of the area that should be mangled. + void check_mangled_unused_area_complete() PRODUCT_RETURN; + + // Mangle the MemRegion. This is a non-space specific mangler. It + // is used during the initial mangling of a space before the space + // is fully constructed. Also is used when a generation is expanded + // and possibly before the spaces have been reshaped to to the new + // size of the generation. + static void mangle_region(MemRegion mr); +}; + +class ContiguousSpace; + +// For use with GenCollectedHeap's +class GenSpaceMangler: public SpaceMangler { + ContiguousSpace* _sp; + + ContiguousSpace* sp() { return _sp; } + + HeapWord* top() const { return _sp->top(); } + HeapWord* end() const { return _sp->end(); } + + public: + GenSpaceMangler(ContiguousSpace* sp) : SpaceMangler(), _sp(sp) {} +}; + +// For use with ParallelScavengeHeap's. +class MutableSpaceMangler: public SpaceMangler { + MutableSpace* _sp; + + MutableSpace* sp() { return _sp; } + + HeapWord* top() const { return _sp->top(); } + HeapWord* end() const { return _sp->end(); } + + public: + MutableSpaceMangler(MutableSpace* sp) : SpaceMangler(), _sp(sp) {} +};