Mercurial > hg > truffle
diff src/share/vm/gc_implementation/g1/heapRegionSeq.hpp @ 3766:c3f1170908be
7045330: G1: Simplify/fix the HeapRegionSeq class
7042285: G1: native memory leak during humongous object allocation
6804436: G1: heap region indices should be size_t
Summary: A series of fixes and improvements to the HeapRegionSeq class: a) replace the _regions growable array with a standard C array, b) avoid de-allocating / re-allocating HeapRegion instances when the heap shrinks / grows (fix for 7042285), c) introduce fast method to map address to HeapRegion via a "biased" array pointer, d) embed the _hrs object in G1CollectedHeap, instead of pointing to it via an indirection, e) assume that all the regions added to the HeapRegionSeq instance are contiguous, f) replace int's with size_t's for indexes (and expand that to HeapRegion as part of 6804436), g) remove unnecessary / unused methods, h) rename a couple of fields (_alloc_search_start and _seq_bottom), i) fix iterate_from() not to always start from index 0 irrespective of the region passed to it, j) add a verification method to check the HeapRegionSeq assumptions, k) always call the wrappers for _hrs.iterate(), _hrs_length(), and _hrs.at() from G1CollectedHeap, not those methods directly, and l) unify the code that expands the sequence (by either re-using or creating a new HeapRegion) and make it robust wrt to a HeapRegion allocation failing.
Reviewed-by: stefank, johnc, brutisso
author | tonyp |
---|---|
date | Fri, 10 Jun 2011 13:16:40 -0400 |
parents | 1216415d8e35 |
children | 4f93f0d00802 |
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--- a/src/share/vm/gc_implementation/g1/heapRegionSeq.hpp Wed Jun 08 21:48:38 2011 -0400 +++ b/src/share/vm/gc_implementation/g1/heapRegionSeq.hpp Fri Jun 10 13:16:40 2011 -0400 @@ -25,92 +25,143 @@ #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP -#include "gc_implementation/g1/heapRegion.hpp" -#include "utilities/growableArray.hpp" - class HeapRegion; class HeapRegionClosure; +class FreeRegionList; + +#define G1_NULL_HRS_INDEX ((size_t) -1) + +// This class keeps track of the region metadata (i.e., HeapRegion +// instances). They are kept in the _regions array in address +// order. A region's index in the array corresponds to its index in +// the heap (i.e., 0 is the region at the bottom of the heap, 1 is +// the one after it, etc.). Two regions that are consecutive in the +// array should also be adjacent in the address space (i.e., +// region(i).end() == region(i+1).bottom(). +// +// We create a HeapRegion when we commit the region's address space +// for the first time. When we uncommit the address space of a +// region we retain the HeapRegion to be able to re-use it in the +// future (in case we recommit it). +// +// We keep track of three lengths: +// +// * _length (returned by length()) is the number of currently +// committed regions. +// * _allocated_length (not exposed outside this class) is the +// number of regions for which we have HeapRegions. +// * _max_length (returned by max_length()) is the maximum number of +// regions the heap can have. +// +// and maintain that: _length <= _allocated_length <= _max_length class HeapRegionSeq: public CHeapObj { - // _regions is kept sorted by start address order, and no two regions are - // overlapping. - GrowableArray<HeapRegion*> _regions; + // The array that holds the HeapRegions. + HeapRegion** _regions; + + // Version of _regions biased to address 0 + HeapRegion** _regions_biased; + + // The number of regions committed in the heap. + size_t _length; - // The index in "_regions" at which to start the next allocation search. - // (For efficiency only; private to obj_allocate after initialization.) - int _alloc_search_start; + // The address of the first reserved word in the heap. + HeapWord* _heap_bottom; + + // The address of the last reserved word in the heap - 1. + HeapWord* _heap_end; + + // The log of the region byte size. + size_t _region_shift; + + // A hint for which index to start searching from for humongous + // allocations. + size_t _next_search_index; - // Finds a contiguous set of empty regions of length num, starting - // from a given index. - int find_contiguous_from(int from, size_t num); + // The number of regions for which we have allocated HeapRegions for. + size_t _allocated_length; + + // The maximum number of regions in the heap. + size_t _max_length; + + // Find a contiguous set of empty regions of length num, starting + // from the given index. + size_t find_contiguous_from(size_t from, size_t num); - // Currently, we're choosing collection sets in a round-robin fashion, - // starting here. - int _next_rr_candidate; + // Map a heap address to a biased region index. Assume that the + // address is valid. + inline size_t addr_to_index_biased(HeapWord* addr) const; - // The bottom address of the bottom-most region, or else NULL if there - // are no regions in the sequence. - char* _seq_bottom; + void increment_length(size_t* length) { + assert(*length < _max_length, "pre-condition"); + *length += 1; + } + + void decrement_length(size_t* length) { + assert(*length > 0, "pre-condition"); + *length -= 1; + } public: - // Initializes "this" to the empty sequence of regions. - HeapRegionSeq(const size_t max_size); + // Empty contructor, we'll initialize it with the initialize() method. + HeapRegionSeq() { } + + void initialize(HeapWord* bottom, HeapWord* end, size_t max_length); - // Adds "hr" to "this" sequence. Requires "hr" not to overlap with - // any region already in "this". (Will perform better if regions are - // inserted in ascending address order.) - void insert(HeapRegion* hr); + // Return the HeapRegion at the given index. Assume that the index + // is valid. + inline HeapRegion* at(size_t index) const; + + // If addr is within the committed space return its corresponding + // HeapRegion, otherwise return NULL. + inline HeapRegion* addr_to_region(HeapWord* addr) const; + + // Return the HeapRegion that corresponds to the given + // address. Assume the address is valid. + inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const; - // Given a HeapRegion*, returns its index within _regions, - // or returns -1 if not found. - int find(HeapRegion* hr); + // Return the number of regions that have been committed in the heap. + size_t length() const { return _length; } + + // Return the maximum number of regions in the heap. + size_t max_length() const { return _max_length; } - // Requires the index to be valid, and return the region at the index. - HeapRegion* at(size_t i) { return _regions.at((int)i); } + // Expand the sequence to reflect that the heap has grown from + // old_end to new_end. Either create new HeapRegions, or re-use + // existing ones, and return them in the given list. Returns the + // memory region that covers the newly-created regions. If a + // HeapRegion allocation fails, the result memory region might be + // smaller than the desired one. + MemRegion expand_by(HeapWord* old_end, HeapWord* new_end, + FreeRegionList* list); - // Return the number of regions in the sequence. - size_t length(); - - // Returns the number of contiguous regions at the end of the sequence + // Return the number of contiguous regions at the end of the sequence // that are available for allocation. size_t free_suffix(); // Find a contiguous set of empty regions of length num and return - // the index of the first region or -1 if the search was unsuccessful. - int find_contiguous(size_t num); + // the index of the first region or G1_NULL_HRS_INDEX if the + // search was unsuccessful. + size_t find_contiguous(size_t num); - // Apply the "doHeapRegion" method of "blk" to all regions in "this", - // in address order, terminating the iteration early - // if the "doHeapRegion" method returns "true". - void iterate(HeapRegionClosure* blk); - - // Apply the "doHeapRegion" method of "blk" to all regions in "this", - // starting at "r" (or first region, if "r" is NULL), in a circular - // manner, terminating the iteration early if the "doHeapRegion" method - // returns "true". - void iterate_from(HeapRegion* r, HeapRegionClosure* blk); + // Apply blk->doHeapRegion() on all committed regions in address order, + // terminating the iteration early if doHeapRegion() returns true. + void iterate(HeapRegionClosure* blk) const; - // As above, but start from a given index in the sequence - // instead of a given heap region. - void iterate_from(int idx, HeapRegionClosure* blk); + // As above, but start the iteration from hr and loop around. If hr + // is NULL, we start from the first region in the heap. + void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const; - // Requires "shrink_bytes" to be a multiple of the page size and heap - // region granularity. Deletes as many "rightmost" completely free heap - // regions from the sequence as comprise shrink_bytes bytes. Returns the - // MemRegion indicating the region those regions comprised, and sets - // "num_regions_deleted" to the number of regions deleted. - MemRegion shrink_by(size_t shrink_bytes, size_t& num_regions_deleted); + // Tag as uncommitted as many regions that are completely free as + // possible, up to shrink_bytes, from the suffix of the committed + // sequence. Return a MemRegion that corresponds to the address + // range of the uncommitted regions. Assume shrink_bytes is page and + // heap region aligned. + MemRegion shrink_by(size_t shrink_bytes, size_t* num_regions_deleted); - // If "addr" falls within a region in the sequence, return that region, - // or else NULL. - inline HeapRegion* addr_to_region(const void* addr); - - void print(); - - // Prints out runs of empty regions. - void print_empty_runs(); - + // Do some sanity checking. + void verify_optional() PRODUCT_RETURN; }; #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP