90 // _klass_range_start _klass_range_end encoding end
91 // |//////////|///////////////////////////| |
92 // |///CDS////|////1gb class space////////| ... ... |
93 // |//////////|///////////////////////////| |
94 // | | |
95 // 0x8_0000_0000 0x8_4800_0000 0x9_0000_0000
96 //
97
98 // If compressed klass pointers then use narrowKlass.
99 typedef juint narrowKlass;
100
101 class CompressedKlassPointers : public AllStatic {
102 friend class VMStructs;
103 friend class ArchiveBuilder;
104
105 // We use a different narrow Klass pointer geometry depending on
106 // whether we run in standard mode or in compact-object-header-mode.
107
108 // Narrow klass pointer bits for an unshifted narrow Klass pointer.
109 static constexpr int narrow_klass_pointer_bits_noncoh = 32;
110 static constexpr int narrow_klass_pointer_bits_coh = 22;
111
112 // Bit size of a narrowKlass
113 static int _narrow_klass_pointer_bits;
114
115 // The maximum shift values we can use depending on UseCompactObjectHeaders
116 static constexpr int max_shift_noncoh = 3;
117 static constexpr int max_shift_coh = 10;
118
119 // Maximum shift usable
120 static int _max_shift;
121
122 // Encoding Base, Encoding Shift
123 static address _base;
124 static int _shift;
125
126 // Start and end of the Klass Range. Start includes the protection zone if one exists.
127 // Note: guaranteed to be aligned to 1<<shift (klass_alignment_in_bytes)
128 static address _klass_range_start;
129 static address _klass_range_end;
130
169 // 4) call reserve_address_space_for_compressed_classes() either from CDS initialization or, if CDS is off,
170 // from metaspace initialization. Reserves space for class space + CDS, attempts to reserve such that
171 // we later can use a "good" encoding scheme. Reservation is highly CPU-specific.
172 // 5) Initialize the narrow Klass encoding scheme by determining encoding base and shift:
173 // 5a) if CDS=on: Calls initialize_for_given_encoding() with the reservation base from step (4) and the
174 // CDS-intrinsic setting for shift; here, we don't have any freedom to deviate from the base.
175 // 5b) if CDS=off: Calls initialize() - here, we have more freedom and, if we want, can choose an encoding
176 // base that differs from the reservation base from step (4). That allows us, e.g., to later use
177 // zero-based encoding.
178 // 6) ... from now on, we can use base() and shift().
179
180 // Called right after argument parsing; defines narrow klass pointer geometry limits
181 static void pre_initialize();
182
183 // The number of bits a narrow Klass pointer has;
184 static int narrow_klass_pointer_bits() { check_init(_narrow_klass_pointer_bits); return _narrow_klass_pointer_bits; }
185
186 // The maximum possible shift; the actual shift employed later can be smaller (see initialize())
187 static int max_shift() { check_init(_max_shift); return _max_shift; }
188
189 // Returns the maximum allowed klass range size. It is calculated from the length of the encoding range
190 // resulting from the current encoding settings (base, shift), capped to a certain max. value.
191 static size_t max_klass_range_size();
192
193 // Reserve a range of memory that is to contain Klass strucutures which are referenced by narrow Klass IDs.
194 // If optimize_for_zero_base is true, the implementation will attempt to reserve optimized for zero-based encoding.
195 static char* reserve_address_space_for_compressed_classes(size_t size, bool aslr, bool optimize_for_zero_base);
196
197 // Given a klass range [addr, addr+len) and a given encoding scheme, assert that this scheme covers the range, then
198 // set this encoding scheme. Used by CDS at runtime to re-instate the scheme used to pre-compute klass ids for
199 // archived heap objects. In this case, we don't have the freedom to choose base and shift; they are handed to
200 // us from CDS.
201 // Note: CDS with +UCCP for 32-bit currently unsupported.
202 static void initialize_for_given_encoding(address addr, size_t len, address requested_base, int requested_shift);
203
204 // Given an address range [addr, addr+len) which the encoding is supposed to
205 // cover, choose base, shift and range.
206 // The address range is the expected range of uncompressed Klass pointers we
207 // will encounter (and the implicit promise that there will be no Klass
208 // structures outside this range).
209 static void initialize(address addr, size_t len);
210
|
90 // _klass_range_start _klass_range_end encoding end
91 // |//////////|///////////////////////////| |
92 // |///CDS////|////1gb class space////////| ... ... |
93 // |//////////|///////////////////////////| |
94 // | | |
95 // 0x8_0000_0000 0x8_4800_0000 0x9_0000_0000
96 //
97
98 // If compressed klass pointers then use narrowKlass.
99 typedef juint narrowKlass;
100
101 class CompressedKlassPointers : public AllStatic {
102 friend class VMStructs;
103 friend class ArchiveBuilder;
104
105 // We use a different narrow Klass pointer geometry depending on
106 // whether we run in standard mode or in compact-object-header-mode.
107
108 // Narrow klass pointer bits for an unshifted narrow Klass pointer.
109 static constexpr int narrow_klass_pointer_bits_noncoh = 32;
110 static constexpr int narrow_klass_pointer_bits_coh = 19;
111
112 // Bit size of a narrowKlass
113 static int _narrow_klass_pointer_bits;
114
115 // The maximum shift values we can use depending on UseCompactObjectHeaders
116 static constexpr int max_shift_noncoh = 3;
117 static constexpr int max_shift_coh = 10;
118
119 // Maximum shift usable
120 static int _max_shift;
121
122 // Encoding Base, Encoding Shift
123 static address _base;
124 static int _shift;
125
126 // Start and end of the Klass Range. Start includes the protection zone if one exists.
127 // Note: guaranteed to be aligned to 1<<shift (klass_alignment_in_bytes)
128 static address _klass_range_start;
129 static address _klass_range_end;
130
169 // 4) call reserve_address_space_for_compressed_classes() either from CDS initialization or, if CDS is off,
170 // from metaspace initialization. Reserves space for class space + CDS, attempts to reserve such that
171 // we later can use a "good" encoding scheme. Reservation is highly CPU-specific.
172 // 5) Initialize the narrow Klass encoding scheme by determining encoding base and shift:
173 // 5a) if CDS=on: Calls initialize_for_given_encoding() with the reservation base from step (4) and the
174 // CDS-intrinsic setting for shift; here, we don't have any freedom to deviate from the base.
175 // 5b) if CDS=off: Calls initialize() - here, we have more freedom and, if we want, can choose an encoding
176 // base that differs from the reservation base from step (4). That allows us, e.g., to later use
177 // zero-based encoding.
178 // 6) ... from now on, we can use base() and shift().
179
180 // Called right after argument parsing; defines narrow klass pointer geometry limits
181 static void pre_initialize();
182
183 // The number of bits a narrow Klass pointer has;
184 static int narrow_klass_pointer_bits() { check_init(_narrow_klass_pointer_bits); return _narrow_klass_pointer_bits; }
185
186 // The maximum possible shift; the actual shift employed later can be smaller (see initialize())
187 static int max_shift() { check_init(_max_shift); return _max_shift; }
188
189 // Returns the maximum encoding range, given the current geometry (narrow klass bit size and shift)
190 static size_t max_encoding_range_size() { return nth_bit(narrow_klass_pointer_bits() + max_shift()); }
191
192 // For use before pre-initialization
193 static constexpr size_t max_klass_range_size_coh = nth_bit(narrow_klass_pointer_bits_coh + max_shift_coh);
194
195 // Returns the maximum allowed klass range size.
196 static size_t max_klass_range_size();
197
198 // Reserve a range of memory that is to contain Klass strucutures which are referenced by narrow Klass IDs.
199 // If optimize_for_zero_base is true, the implementation will attempt to reserve optimized for zero-based encoding.
200 static char* reserve_address_space_for_compressed_classes(size_t size, bool aslr, bool optimize_for_zero_base);
201
202 // Given a klass range [addr, addr+len) and a given encoding scheme, assert that this scheme covers the range, then
203 // set this encoding scheme. Used by CDS at runtime to re-instate the scheme used to pre-compute klass ids for
204 // archived heap objects. In this case, we don't have the freedom to choose base and shift; they are handed to
205 // us from CDS.
206 // Note: CDS with +UCCP for 32-bit currently unsupported.
207 static void initialize_for_given_encoding(address addr, size_t len, address requested_base, int requested_shift);
208
209 // Given an address range [addr, addr+len) which the encoding is supposed to
210 // cover, choose base, shift and range.
211 // The address range is the expected range of uncompressed Klass pointers we
212 // will encounter (and the implicit promise that there will be no Klass
213 // structures outside this range).
214 static void initialize(address addr, size_t len);
215
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