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src/share/vm/gc_implementation/g1/g1PageBasedVirtualSpace.hpp
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rev 7696 : 8058354: SPECjvm2008-Derby -2.7% performance regression on Solaris-X64 starting with 9-b29
Summary: Allow partial use of large pages for auxiliary data structures in G1.
Reviewed-by:
@@ -32,21 +32,26 @@
// Virtual space management helper for a virtual space with an OS page allocation
// granularity.
// (De-)Allocation requests are always OS page aligned by passing a page index
// and multiples of pages.
+// We only support reservations which base address is aligned to a given commit
+// size. The length of the area managed need not commit size aligned (but OS default
+// page size aligned) because some OSes cannot provide a an os_commit_size aligned
+// reservation without also being size-aligned. Any tail area is committed using OS
+// small pages.
// The implementation gives an error when trying to commit or uncommit pages that
// have already been committed or uncommitted.
class G1PageBasedVirtualSpace VALUE_OBJ_CLASS_SPEC {
friend class VMStructs;
private:
// Reserved area addresses.
char* _low_boundary;
char* _high_boundary;
- // The commit/uncommit granularity in bytes.
- size_t _page_size;
+ // The preferred commit/uncommit granularity in bytes.
+ size_t _commit_size;
// Bitmap used for verification of commit/uncommit operations.
BitMap _committed;
// Bitmap used to keep track of which pages are dirty or not for _special
@@ -60,16 +65,23 @@
bool _special;
// Indicates whether the committed space should be executable.
bool _executable;
+ // Commit the given memory range by using _commit_size pages as much as possible
+ // and the remainder with small sized pages. The start address must be _commit_size
+ // aligned.
+ void commit_int(char* start, char* end);
+ // Uncommit the given memory range.
+ void uncommit_int(char* start, char* end);
+
// Returns the index of the page which contains the given address.
uintptr_t addr_to_page_index(char* addr) const;
// Returns the address of the given page index.
char* page_start(uintptr_t index);
- // Returns the byte size of the given number of pages.
- size_t byte_size_for_pages(size_t num);
+ // Returns the address of the given page index ranging from 0..size_in_pages-1.
+ char* page_end(uintptr_t index);
// Returns true if the entire area is backed by committed memory.
bool is_area_committed(uintptr_t start, size_t size_in_pages) const;
// Returns true if the entire area is not backed by committed memory.
bool is_area_uncommitted(uintptr_t start, size_t size_in_pages) const;
@@ -83,11 +95,13 @@
// Uncommit the given area of pages starting at start being size_in_pages large.
void uncommit(uintptr_t start, size_t size_in_pages);
// Initialization
G1PageBasedVirtualSpace();
- bool initialize_with_granularity(ReservedSpace rs, size_t page_size);
+ // Initialize the given reserved space with the given base address and actual size.
+ // Prefer to commit in commit_size chunks.
+ bool initialize_with_granularity(ReservedSpace rs, size_t actual_size, size_t commit_size);
// Destruction
~G1PageBasedVirtualSpace();
// Amount of reserved memory.
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