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src/hotspot/share/gc/shared/stringdedup/stringDedup.hpp
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@@ -1,7 +1,7 @@
/*
- * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, Oracle and/or its affiliates. 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.
@@ -20,12 +20,12 @@
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
-#ifndef SHARE_VM_GC_G1_G1STRINGDEDUP_HPP
-#define SHARE_VM_GC_G1_G1STRINGDEDUP_HPP
+#ifndef SHARE_VM_GC_SHARED_STRINGDEDUP_STRINGDEDUP_HPP
+#define SHARE_VM_GC_SHARED_STRINGDEDUP_STRINGDEDUP_HPP
//
// String Deduplication
//
// String deduplication aims to reduce the heap live-set by deduplicating identical
@@ -47,30 +47,11 @@
// String object is adjusted to point to that character array, releasing the reference
// to the original array allowing it to eventually be garbage collected. If the lookup
// fails the character array is instead inserted into the hashtable so that this array
// can be shared at some point in the future.
//
-// Candidate selection
-//
-// An object is considered a deduplication candidate if all of the following
-// statements are true:
-//
-// - The object is an instance of java.lang.String
-//
-// - The object is being evacuated from a young heap region
-//
-// - The object is being evacuated to a young/survivor heap region and the
-// object's age is equal to the deduplication age threshold
-//
-// or
-//
-// The object is being evacuated to an old heap region and the object's age is
-// less than the deduplication age threshold
-//
-// Once an string object has been promoted to an old region, or its age is higher
-// than the deduplication age threshold, is will never become a candidate again.
-// This approach avoids making the same object a candidate more than once.
+// Candidate selection criteria is GC specific.
//
// Interned strings are a bit special. They are explicitly deduplicated just before
// being inserted into the StringTable (to avoid counteracting C2 optimizations done
// on string literals), then they also become deduplication candidates if they reach
// the deduplication age threshold or are evacuated to an old heap region. The second
@@ -80,110 +61,67 @@
//
// For additional information on string deduplication, please see JEP 192,
// http://openjdk.java.net/jeps/192
//
+#include "gc/shared/stringdedup/stringDedupQueue.hpp"
+#include "gc/shared/stringdedup/stringDedupStat.hpp"
+#include "gc/shared/stringdedup/stringDedupTable.hpp"
#include "memory/allocation.hpp"
-#include "oops/oop.hpp"
-
-class OopClosure;
-class BoolObjectClosure;
-class ThreadClosure;
-class outputStream;
-class G1StringDedupTable;
-class G1StringDedupUnlinkOrOopsDoClosure;
-class G1GCPhaseTimes;
+#include "runtime/thread.hpp"
//
// Main interface for interacting with string deduplication.
//
-class G1StringDedup : public AllStatic {
+class StringDedup : public AllStatic {
private:
- // Single state for checking if both G1 and string deduplication is enabled.
+ // Single state for checking if string deduplication is enabled.
static bool _enabled;
- // Candidate selection policies, returns true if the given object is
- // candidate for string deduplication.
- static bool is_candidate_from_mark(oop obj);
- static bool is_candidate_from_evacuation(bool from_young, bool to_young, oop obj);
-
public:
- // Returns true if both G1 and string deduplication is enabled.
+ // Returns true if string deduplication is enabled.
static bool is_enabled() {
return _enabled;
}
- // Initialize string deduplication.
- static void initialize();
-
// Stop the deduplication thread.
static void stop();
// Immediately deduplicates the given String object, bypassing the
// the deduplication queue.
static void deduplicate(oop java_string);
- // Enqueues a deduplication candidate for later processing by the deduplication
- // thread. Before enqueuing, these functions apply the appropriate candidate
- // selection policy to filters out non-candidates.
- static void enqueue_from_mark(oop java_string, uint worker_id);
- static void enqueue_from_evacuation(bool from_young, bool to_young,
- unsigned int queue, oop java_string);
-
- static void oops_do(OopClosure* keep_alive);
- static void parallel_unlink(G1StringDedupUnlinkOrOopsDoClosure* unlink, uint worker_id);
- static void unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* keep_alive,
- bool allow_resize_and_rehash, G1GCPhaseTimes* phase_times = NULL);
+ static void parallel_unlink(StringDedupUnlinkOrOopsDoClosure* unlink, uint worker_id);
static void threads_do(ThreadClosure* tc);
static void print_worker_threads_on(outputStream* st);
static void verify();
+
+ // GC support
+ static void gc_prologue(bool resize_and_rehash_table);
+ static void gc_epilogue();
+
+protected:
+ // Initialize string deduplication.
+ // QUEUE: String Dedup Queue implementation
+ // STAT: String Dedup Stat implementation
+ template <typename QUEUE, typename STAT>
+ static void initialize_impl();
};
//
-// This closure encapsulates the state and the closures needed when scanning
+// This closure encapsulates the closures needed when scanning
// the deduplication queue and table during the unlink_or_oops_do() operation.
-// A single instance of this closure is created and then shared by all worker
-// threads participating in the scan. The _next_queue and _next_bucket fields
-// provide a simple mechanism for GC workers to claim exclusive access to a
-// queue or a table partition.
//
-class G1StringDedupUnlinkOrOopsDoClosure : public StackObj {
+class StringDedupUnlinkOrOopsDoClosure : public StackObj {
private:
BoolObjectClosure* _is_alive;
OopClosure* _keep_alive;
- G1StringDedupTable* _resized_table;
- G1StringDedupTable* _rehashed_table;
- size_t _next_queue;
- size_t _next_bucket;
public:
- G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
- OopClosure* keep_alive,
- bool allow_resize_and_rehash);
- ~G1StringDedupUnlinkOrOopsDoClosure();
-
- bool is_resizing() {
- return _resized_table != NULL;
- }
-
- G1StringDedupTable* resized_table() {
- return _resized_table;
- }
-
- bool is_rehashing() {
- return _rehashed_table != NULL;
- }
-
- // Atomically claims the next available queue for exclusive access by
- // the current thread. Returns the queue number of the claimed queue.
- size_t claim_queue();
-
- // Atomically claims the next available table partition for exclusive
- // access by the current thread. Returns the table bucket number where
- // the claimed partition starts.
- size_t claim_table_partition(size_t partition_size);
+ StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
+ OopClosure* keep_alive);
// Applies and returns the result from the is_alive closure, or
// returns true if no such closure was provided.
bool is_alive(oop o) {
if (_is_alive != NULL) {
@@ -199,6 +137,6 @@
_keep_alive->do_oop(p);
}
}
};
-#endif // SHARE_VM_GC_G1_G1STRINGDEDUP_HPP
+#endif // SHARE_VM_GC_SHARED_STRINGDEDUP_STRINGDEDUP_HPP
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