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src/hotspot/share/cds/aotMetaspace.cpp

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1938   //  with narrow class pointers.
1939   // We reserve the whole range spanning both spaces, then split that range up.
1940 
1941   const size_t class_space_alignment = Metaspace::reserve_alignment();
1942 
1943   // When running with class space, requested archive base must satisfy both cds core alignment
1944   // and class space alignment.
1945   const size_t base_address_alignment = MAX2(class_space_alignment, archive_space_alignment);
1946   assert(is_aligned(base_address, base_address_alignment),
1947            "Archive base address unaligned: " PTR_FORMAT ", needs alignment: %zu.",
1948            p2i(base_address), base_address_alignment);
1949 
1950   size_t class_space_size = CompressedClassSpaceSize;
1951   assert(CompressedClassSpaceSize > 0 &&
1952          is_aligned(CompressedClassSpaceSize, class_space_alignment),
1953          "CompressedClassSpaceSize malformed: %zu", CompressedClassSpaceSize);
1954 
1955   const size_t ccs_begin_offset = align_up(archive_space_size, class_space_alignment);
1956   const size_t gap_size = ccs_begin_offset - archive_space_size;
1957 
1958   // Reduce class space size if it would not fit into the Klass encoding range
1959   constexpr size_t max_encoding_range_size = 4 * G;

1960   guarantee(archive_space_size < max_encoding_range_size - class_space_alignment, "Archive too large");
1961   if ((archive_space_size + gap_size + class_space_size) > max_encoding_range_size) {
1962     class_space_size = align_down(max_encoding_range_size - archive_space_size - gap_size, class_space_alignment);
1963     log_info(metaspace)("CDS initialization: reducing class space size from %zu to %zu",
1964         CompressedClassSpaceSize, class_space_size);
1965     FLAG_SET_ERGO(CompressedClassSpaceSize, class_space_size);
1966   }
1967 
1968   const size_t total_range_size =
1969       archive_space_size + gap_size + class_space_size;
1970 
1971   // Test that class space base address plus shift can be decoded by aarch64, when restored.
1972   const int precomputed_narrow_klass_shift = ArchiveBuilder::precomputed_narrow_klass_shift();
1973   if (!CompressedKlassPointers::check_klass_decode_mode(base_address, precomputed_narrow_klass_shift,
1974                                                         total_range_size)) {
1975     aot_log_info(aot)("CDS initialization: Cannot use SharedBaseAddress " PTR_FORMAT " with precomputed shift %d.",
1976                   p2i(base_address), precomputed_narrow_klass_shift);
1977     use_archive_base_addr = false;
1978   }
1979 

1938   //  with narrow class pointers.
1939   // We reserve the whole range spanning both spaces, then split that range up.
1940 
1941   const size_t class_space_alignment = Metaspace::reserve_alignment();
1942 
1943   // When running with class space, requested archive base must satisfy both cds core alignment
1944   // and class space alignment.
1945   const size_t base_address_alignment = MAX2(class_space_alignment, archive_space_alignment);
1946   assert(is_aligned(base_address, base_address_alignment),
1947            "Archive base address unaligned: " PTR_FORMAT ", needs alignment: %zu.",
1948            p2i(base_address), base_address_alignment);
1949 
1950   size_t class_space_size = CompressedClassSpaceSize;
1951   assert(CompressedClassSpaceSize > 0 &&
1952          is_aligned(CompressedClassSpaceSize, class_space_alignment),
1953          "CompressedClassSpaceSize malformed: %zu", CompressedClassSpaceSize);
1954 
1955   const size_t ccs_begin_offset = align_up(archive_space_size, class_space_alignment);
1956   const size_t gap_size = ccs_begin_offset - archive_space_size;
1957 
1958   // Reduce class space size if it would not fit into the maximum possible Klass encoding range. That
1959   // range is defined by the narrowKlass size.
1960   const size_t max_encoding_range_size = CompressedKlassPointers::max_klass_range_size();
1961   guarantee(archive_space_size < max_encoding_range_size - class_space_alignment, "Archive too large");
1962   if ((archive_space_size + gap_size + class_space_size) > max_encoding_range_size) {
1963     class_space_size = align_down(max_encoding_range_size - archive_space_size - gap_size, class_space_alignment);
1964     log_info(metaspace)("CDS initialization: reducing class space size from %zu to %zu",
1965         CompressedClassSpaceSize, class_space_size);
1966     FLAG_SET_ERGO(CompressedClassSpaceSize, class_space_size);
1967   }
1968 
1969   const size_t total_range_size =
1970       archive_space_size + gap_size + class_space_size;
1971 
1972   // Test that class space base address plus shift can be decoded by aarch64, when restored.
1973   const int precomputed_narrow_klass_shift = ArchiveBuilder::precomputed_narrow_klass_shift();
1974   if (!CompressedKlassPointers::check_klass_decode_mode(base_address, precomputed_narrow_klass_shift,
1975                                                         total_range_size)) {
1976     aot_log_info(aot)("CDS initialization: Cannot use SharedBaseAddress " PTR_FORMAT " with precomputed shift %d.",
1977                   p2i(base_address), precomputed_narrow_klass_shift);
1978     use_archive_base_addr = false;
1979   }
1980 
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