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src/hotspot/share/cds/metaspaceShared.cpp

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1741   //  with narrow class pointers.
1742   // We reserve the whole range spanning both spaces, then split that range up.
1743 
1744   const size_t class_space_alignment = Metaspace::reserve_alignment();
1745 
1746   // When running with class space, requested archive base must satisfy both cds core alignment
1747   // and class space alignment.
1748   const size_t base_address_alignment = MAX2(class_space_alignment, archive_space_alignment);
1749   assert(is_aligned(base_address, base_address_alignment),
1750            "Archive base address unaligned: " PTR_FORMAT ", needs alignment: %zu.",
1751            p2i(base_address), base_address_alignment);
1752 
1753   size_t class_space_size = CompressedClassSpaceSize;
1754   assert(CompressedClassSpaceSize > 0 &&
1755          is_aligned(CompressedClassSpaceSize, class_space_alignment),
1756          "CompressedClassSpaceSize malformed: %zu", CompressedClassSpaceSize);
1757 
1758   const size_t ccs_begin_offset = align_up(archive_space_size, class_space_alignment);
1759   const size_t gap_size = ccs_begin_offset - archive_space_size;
1760 
1761   // Reduce class space size if it would not fit into the Klass encoding range
1762   constexpr size_t max_encoding_range_size = 4 * G;

1763   guarantee(archive_space_size < max_encoding_range_size - class_space_alignment, "Archive too large");
1764   if ((archive_space_size + gap_size + class_space_size) > max_encoding_range_size) {
1765     class_space_size = align_down(max_encoding_range_size - archive_space_size - gap_size, class_space_alignment);
1766     log_info(metaspace)("CDS initialization: reducing class space size from %zu to %zu",
1767         CompressedClassSpaceSize, class_space_size);
1768     FLAG_SET_ERGO(CompressedClassSpaceSize, class_space_size);
1769   }
1770 
1771   const size_t total_range_size =
1772       archive_space_size + gap_size + class_space_size;
1773 
1774   // Test that class space base address plus shift can be decoded by aarch64, when restored.
1775   const int precomputed_narrow_klass_shift = ArchiveBuilder::precomputed_narrow_klass_shift();
1776   if (!CompressedKlassPointers::check_klass_decode_mode(base_address, precomputed_narrow_klass_shift,
1777                                                         total_range_size)) {
1778     aot_log_info(aot)("CDS initialization: Cannot use SharedBaseAddress " PTR_FORMAT " with precomputed shift %d.",
1779                   p2i(base_address), precomputed_narrow_klass_shift);
1780     use_archive_base_addr = false;
1781   }
1782 

1741   //  with narrow class pointers.
1742   // We reserve the whole range spanning both spaces, then split that range up.
1743 
1744   const size_t class_space_alignment = Metaspace::reserve_alignment();
1745 
1746   // When running with class space, requested archive base must satisfy both cds core alignment
1747   // and class space alignment.
1748   const size_t base_address_alignment = MAX2(class_space_alignment, archive_space_alignment);
1749   assert(is_aligned(base_address, base_address_alignment),
1750            "Archive base address unaligned: " PTR_FORMAT ", needs alignment: %zu.",
1751            p2i(base_address), base_address_alignment);
1752 
1753   size_t class_space_size = CompressedClassSpaceSize;
1754   assert(CompressedClassSpaceSize > 0 &&
1755          is_aligned(CompressedClassSpaceSize, class_space_alignment),
1756          "CompressedClassSpaceSize malformed: %zu", CompressedClassSpaceSize);
1757 
1758   const size_t ccs_begin_offset = align_up(archive_space_size, class_space_alignment);
1759   const size_t gap_size = ccs_begin_offset - archive_space_size;
1760 
1761   // Reduce class space size if it would not fit into the maximum possible Klass encoding range. That
1762   // range is defined by the narrowKlass size.
1763   const size_t max_encoding_range_size = CompressedKlassPointers::max_klass_range_size();
1764   guarantee(archive_space_size < max_encoding_range_size - class_space_alignment, "Archive too large");
1765   if ((archive_space_size + gap_size + class_space_size) > max_encoding_range_size) {
1766     class_space_size = align_down(max_encoding_range_size - archive_space_size - gap_size, class_space_alignment);
1767     log_info(metaspace)("CDS initialization: reducing class space size from %zu to %zu",
1768         CompressedClassSpaceSize, class_space_size);
1769     FLAG_SET_ERGO(CompressedClassSpaceSize, class_space_size);
1770   }
1771 
1772   const size_t total_range_size =
1773       archive_space_size + gap_size + class_space_size;
1774 
1775   // Test that class space base address plus shift can be decoded by aarch64, when restored.
1776   const int precomputed_narrow_klass_shift = ArchiveBuilder::precomputed_narrow_klass_shift();
1777   if (!CompressedKlassPointers::check_klass_decode_mode(base_address, precomputed_narrow_klass_shift,
1778                                                         total_range_size)) {
1779     aot_log_info(aot)("CDS initialization: Cannot use SharedBaseAddress " PTR_FORMAT " with precomputed shift %d.",
1780                   p2i(base_address), precomputed_narrow_klass_shift);
1781     use_archive_base_addr = false;
1782   }
1783 
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