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src/share/vm/classfile/stringTable.cpp
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@@ -36,10 +36,11 @@
#include "runtime/atomic.inline.hpp"
#include "runtime/mutexLocker.hpp"
#include "utilities/hashtable.inline.hpp"
#include "utilities/macros.hpp"
#if INCLUDE_ALL_GCS
+#include "gc/g1/g1CollectedHeap.hpp"
#include "gc/g1/g1SATBCardTableModRefBS.hpp"
#include "gc/g1/g1StringDedup.hpp"
#endif
PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
@@ -85,22 +86,31 @@
#endif
// --------------------------------------------------------------------------
StringTable* StringTable::_the_table = NULL;
-
+bool StringTable::_ignore_shared_strings = false;
bool StringTable::_needs_rehashing = false;
volatile int StringTable::_parallel_claimed_idx = 0;
+CompactHashtable<oop, char> StringTable::_shared_table;
+
// Pick hashing algorithm
unsigned int StringTable::hash_string(const jchar* s, int len) {
return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :
java_lang_String::hash_code(s, len);
}
-oop StringTable::lookup(int index, jchar* name,
+oop StringTable::lookup_shared(jchar* name, int len) {
+ // java_lang_String::hash_code() was used to compute hash values in the shared table. Don't
+ // use the hash value from StringTable::hash_string() as it might use alternate hashcode.
+ return _shared_table.lookup((const char*)name,
+ java_lang_String::hash_code(name, len), len);
+}
+
+oop StringTable::lookup_dynamic(int index, jchar* name,
int len, unsigned int hash) {
int count = 0;
for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
count++;
if (l->hash() == hash) {
@@ -138,11 +148,12 @@
}
// Since look-up was done lock-free, we need to check if another
// thread beat us in the race to insert the symbol.
- oop test = lookup(index, name, len, hashValue); // calls lookup(u1*, int)
+ // No need to lookup the shared table from here since the caller (intern()) already did
+ oop test = lookup_dynamic(index, name, len, hashValue); // calls lookup(u1*, int)
if (test != NULL) {
// Entry already added
return test;
}
@@ -170,25 +181,35 @@
}
#endif
}
oop StringTable::lookup(jchar* name, int len) {
+ oop string = lookup_shared(name, len);
+ if (string != NULL) {
+ return string;
+ }
+
unsigned int hash = hash_string(name, len);
int index = the_table()->hash_to_index(hash);
- oop string = the_table()->lookup(index, name, len, hash);
+ string = the_table()->lookup_dynamic(index, name, len, hash);
ensure_string_alive(string);
return string;
}
oop StringTable::intern(Handle string_or_null, jchar* name,
int len, TRAPS) {
+ oop found_string = lookup_shared(name, len);
+ if (found_string != NULL) {
+ return found_string;
+ }
+
unsigned int hashValue = hash_string(name, len);
int index = the_table()->hash_to_index(hashValue);
- oop found_string = the_table()->lookup(index, name, len, hashValue);
+ found_string = the_table()->lookup_dynamic(index, name, len, hashValue);
// Found
if (found_string != NULL) {
ensure_string_alive(found_string);
return found_string;
@@ -609,5 +630,133 @@
return dcmd->_dcmdparser.num_arguments();
} else {
return 0;
}
}
+
+// Sharing
+bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space,
+ CompactHashtableWriter* ch_table) {
+#if INCLUDE_CDS && INCLUDE_ALL_GCS && defined(_LP64) && !defined(_WINDOWS)
+ assert(UseG1GC, "Only support G1 GC");
+ assert(UseCompressedOops && UseCompressedClassPointers,
+ "Only support UseCompressedOops and UseCompressedClassPointers enabled");
+
+ Thread* THREAD = Thread::current();
+ G1CollectedHeap::heap()->begin_record_alloc_range();
+ for (int i = 0; i < the_table()->table_size(); ++i) {
+ HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i);
+ for ( ; bucket != NULL; bucket = bucket->next()) {
+ oop s = (oop)(bucket->literal());
+ unsigned int hash = java_lang_String::hash_code(s);
+ if (hash == 0) {
+ continue;
+ }
+
+ // allocate the new 'value' array first
+ typeArrayOop v = java_lang_String::value(s);
+ int v_len = v->size();
+ typeArrayOop new_v;
+ if (G1CollectedHeap::heap()->is_record_alloc_too_large(v_len)) {
+ continue; // skip the current String. The 'value' array is too large to handle
+ } else {
+ new_v = (typeArrayOop)G1CollectedHeap::heap()->record_mem_allocate(v_len);
+ if (new_v == NULL) {
+ return false; // allocation failed
+ }
+ }
+ // now allocate the new String object
+ int s_len = s->size();
+ oop new_s = (oop)G1CollectedHeap::heap()->record_mem_allocate(s_len);
+ if (new_s == NULL) {
+ return false;
+ }
+
+ s->identity_hash();
+ v->identity_hash();
+
+ // copy the objects' data
+ Copy::aligned_disjoint_words((HeapWord*)s, (HeapWord*)new_s, s_len);
+ Copy::aligned_disjoint_words((HeapWord*)v, (HeapWord*)new_v, v_len);
+
+ // adjust the pointer to the 'value' field in the new String oop. Also pre-compute and set the
+ // 'hash' field. That avoids "write" to the shared strings at runtime by the deduplication process.
+ java_lang_String::set_value_raw(new_s, new_v);
+ if (java_lang_String::hash(new_s) == 0) {
+ java_lang_String::set_hash(new_s, hash);
+ }
+
+ // add to the compact table
+ ch_table->add(hash, new_s);
+ }
+ }
+
+ G1CollectedHeap::heap()->end_record_alloc_range(string_space, os::vm_allocation_granularity());
+ assert(string_space->length() <= 2, "sanity");
+#endif
+ return true;
+}
+
+bool StringTable::copy_compact_table(char** top, char *end, GrowableArray<MemRegion> *string_space,
+ size_t* space_size) {
+#if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
+ if (!(UseG1GC && UseCompressedOops && UseCompressedClassPointers)) {
+ if (PrintSharedSpaces) {
+ tty->print_cr("Shared strings are excluded from the archive as UseG1GC, "
+ "UseCompressedOops and UseCompressedClassPointers are required.");
+ }
+ return true;
+ }
+
+ CompactHashtableWriter ch_table(CompactHashtable<oop, char>::_string_table,
+ the_table()->number_of_entries(),
+ &MetaspaceShared::stats()->string);
+
+ // Copy the interned strings into the "string space" within the java heap
+ if (!copy_shared_string(string_space, &ch_table)) {
+ return false;
+ }
+
+ for (int i = 0; i < string_space->length(); i++) {
+ *space_size += string_space->at(i).byte_size();
+ }
+
+ // Now dump the compact table
+ if (*top + ch_table.get_required_bytes() > end) {
+ // not enough space left
+ return false;
+ }
+ ch_table.dump(top, end);
+ *top = (char*)align_pointer_up(*top, sizeof(void*));
+
+#endif
+ return true;
+}
+
+void StringTable::shared_oops_do(OopClosure* f) {
+#if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
+ _shared_table.oops_do(f);
+#endif
+}
+
+const char* StringTable::init_shared_table(FileMapInfo *mapinfo, char *buffer) {
+#if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
+ if (mapinfo->space_capacity(MetaspaceShared::first_string) == 0) {
+ // no shared string data
+ return buffer;
+ }
+
+ // initialize the shared table
+ juint *p = (juint*)buffer;
+ const char* end = _shared_table.init(
+ CompactHashtable<oop, char>::_string_table, (char*)p);
+ const char* aligned_end = (const char*)align_pointer_up(end, sizeof(void*));
+
+ if (_ignore_shared_strings) {
+ _shared_table.reset();
+ }
+
+ return aligned_end;
+#endif
+
+ return buffer;
+}
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