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8332514: Allow class space size to be larger than 3GB
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Reviewed-by: iklam, dholmes
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@tstuefe
tstuefe committed Jun 3, 2024
1 parent 5ed0d52 commit b101586
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Showing 3 changed files with 132 additions and 52 deletions.
12 changes: 11 additions & 1 deletion src/hotspot/share/cds/metaspaceShared.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1303,7 +1303,7 @@ char* MetaspaceShared::reserve_address_space_for_archives(FileMapInfo* static_ma
"Archive base address unaligned: " PTR_FORMAT ", needs alignment: %zu.",
p2i(base_address), base_address_alignment);

const size_t class_space_size = CompressedClassSpaceSize;
size_t class_space_size = CompressedClassSpaceSize;
assert(CompressedClassSpaceSize > 0 &&
is_aligned(CompressedClassSpaceSize, class_space_alignment),
"CompressedClassSpaceSize malformed: "
Expand All @@ -1312,6 +1312,16 @@ char* MetaspaceShared::reserve_address_space_for_archives(FileMapInfo* static_ma
const size_t ccs_begin_offset = align_up(archive_space_size, class_space_alignment);
const size_t gap_size = ccs_begin_offset - archive_space_size;

// Reduce class space size if it would not fit into the Klass encoding range
constexpr size_t max_encoding_range_size = 4 * G;
guarantee(archive_space_size < max_encoding_range_size - class_space_alignment, "Archive too large");
if ((archive_space_size + gap_size + class_space_size) > max_encoding_range_size) {
class_space_size = align_down(max_encoding_range_size - archive_space_size - gap_size, class_space_alignment);
log_info(metaspace)("CDS initialization: reducing class space size from " SIZE_FORMAT " to " SIZE_FORMAT,
CompressedClassSpaceSize, class_space_size);
FLAG_SET_ERGO(CompressedClassSpaceSize, class_space_size);
}

const size_t total_range_size =
archive_space_size + gap_size + class_space_size;

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2 changes: 1 addition & 1 deletion src/hotspot/share/runtime/globals.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1399,7 +1399,7 @@ const int ObjectAlignmentInBytes = 8;
product(size_t, CompressedClassSpaceSize, 1*G, \
"Maximum size of class area in Metaspace when compressed " \
"class pointers are used") \
range(1*M, 3*G) \
range(1*M, LP64_ONLY(4*G) NOT_LP64(max_uintx)) \
\
develop(size_t, CompressedClassSpaceBaseAddress, 0, \
"Force the class space to be allocated at this address or " \
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170 changes: 120 additions & 50 deletions test/hotspot/jtreg/runtime/CompressedOops/CompressedClassSpaceSize.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,75 +22,145 @@
*/

/*
* @test
* @test id=invalid
* @bug 8022865
* @summary Tests for the -XX:CompressedClassSpaceSize command line option
* @requires vm.bits == 64 & vm.opt.final.UseCompressedOops == true
* @requires vm.flagless
* @library /test/lib
* @modules java.base/jdk.internal.misc
* java.management
* @run driver CompressedClassSpaceSize
* @modules java.base/jdk.internal.misc java.management
* @run driver CompressedClassSpaceSize invalid
*/

/*
* @test id=valid_small
* @bug 8022865
* @summary Tests for the -XX:CompressedClassSpaceSize command line option
* @requires vm.bits == 64 & vm.opt.final.UseCompressedOops == true
* @requires vm.flagless
* @library /test/lib
* @modules java.base/jdk.internal.misc java.management
* @run driver CompressedClassSpaceSize valid_small
*/

/*
* @test id=valid_large_nocds
* @bug 8022865
* @summary Tests for the -XX:CompressedClassSpaceSize command line option
* @requires vm.bits == 64 & vm.opt.final.UseCompressedOops == true
* @requires vm.flagless
* @library /test/lib
* @modules java.base/jdk.internal.misc java.management
* @run driver CompressedClassSpaceSize valid_large_nocds
*/

/*
* @test id=valid_large_cds
* @bug 8022865
* @summary Tests for the -XX:CompressedClassSpaceSize command line option
* @requires vm.bits == 64 & vm.opt.final.UseCompressedOops == true & vm.cds
* @requires vm.flagless
* @library /test/lib
* @modules java.base/jdk.internal.misc java.management
* @run driver CompressedClassSpaceSize valid_large_cds
*/

import jdk.test.lib.process.ProcessTools;
import jdk.test.lib.process.OutputAnalyzer;

public class CompressedClassSpaceSize {

public static void main(String[] args) throws Exception {
ProcessBuilder pb;
OutputAnalyzer output;
// Minimum size is 1MB
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=0",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("outside the allowed range")
.shouldHaveExitValue(1);

// Invalid size of -1 should be handled correctly
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=-1",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("Improperly specified VM option 'CompressedClassSpaceSize=-1'")
.shouldHaveExitValue(1);
final static long MB = 1024 * 1024;

final static long minAllowedClassSpaceSize = MB;
final static long minRealClassSpaceSize = 16 * MB;
final static long maxClassSpaceSize = 4096 * MB;

// Maximum size is 3GB
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=4g",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("outside the allowed range")
.shouldHaveExitValue(1);
// For the valid_large_cds sub test: we need to have a notion of what archive size to
// maximally expect, with a generous fudge factor to avoid having to tweak this test
// ofent. Note: today's default archives are around 16-20 MB.
final static long maxExpectedArchiveSize = 512 * MB;

public static void main(String[] args) throws Exception {
ProcessBuilder pb;
OutputAnalyzer output;

// Make sure the minimum size is set correctly and printed
// (Note: ccs size are rounded up to the next larger root chunk boundary (16m).
// Note that this is **reserved** size and does not affect rss.
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:+UnlockDiagnosticVMOptions",
"-XX:CompressedClassSpaceSize=1m",
"-Xlog:gc+metaspace=trace",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldMatch("Compressed class space.*16777216")
.shouldHaveExitValue(0);
switch (args[0]) {
case "invalid": {
// < Minimum size
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=0",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("outside the allowed range")
.shouldHaveExitValue(1);

// Invalid size of -1 should be handled correctly
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=-1",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("Improperly specified VM option 'CompressedClassSpaceSize=-1'")
.shouldHaveExitValue(1);

// Make sure the maximum size is set correctly and printed
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:+UnlockDiagnosticVMOptions",
"-XX:CompressedClassSpaceSize=3g",
"-Xlog:gc+metaspace=trace",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldMatch("Compressed class space.*3221225472")
.shouldHaveExitValue(0);
// > Maximum size
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=" + maxClassSpaceSize + 1,
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("outside the allowed range")
.shouldHaveExitValue(1);

pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:-UseCompressedClassPointers",
"-XX:CompressedClassSpaceSize=" + minAllowedClassSpaceSize,
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("Setting CompressedClassSpaceSize has no effect when compressed class pointers are not used")
.shouldHaveExitValue(0);
}
break;
case "valid_small": {
// Make sure the minimum size is set correctly and printed
// (Note: ccs size are rounded up to the next larger root chunk boundary (16m).
// Note that this is **reserved** size and does not affect rss.
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:+UnlockDiagnosticVMOptions",
"-XX:CompressedClassSpaceSize=" + minAllowedClassSpaceSize,
"-Xlog:gc+metaspace",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldMatch("Compressed class space.*" + minRealClassSpaceSize)
.shouldHaveExitValue(0);
}
break;
case "valid_large_nocds": {
// Without CDS, we should get 4G
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=" + maxClassSpaceSize,
"-Xshare:off", "-Xlog:metaspace*", "-version");
output = new OutputAnalyzer(pb.start());
output.shouldMatch("Compressed class space.*" + maxClassSpaceSize)
.shouldHaveExitValue(0);
}
break;
case "valid_large_cds": {
// Create archive
pb = ProcessTools.createLimitedTestJavaProcessBuilder(
"-XX:SharedArchiveFile=./abc.jsa", "-Xshare:dump", "-version");
output = new OutputAnalyzer(pb.start());
output.shouldHaveExitValue(0);

pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:-UseCompressedClassPointers",
"-XX:CompressedClassSpaceSize=1m",
"-version");
output = new OutputAnalyzer(pb.start());
output.shouldContain("Setting CompressedClassSpaceSize has no effect when compressed class pointers are not used")
.shouldHaveExitValue(0);
// With CDS, class space should fill whatever the CDS archive leaves us (modulo alignment)
pb = ProcessTools.createLimitedTestJavaProcessBuilder("-XX:CompressedClassSpaceSize=" + maxClassSpaceSize,
"-XX:SharedArchiveFile=./abc.jsa", "-Xshare:on", "-Xlog:metaspace*", "-version");
output = new OutputAnalyzer(pb.start());
output.shouldHaveExitValue(0);
long reducedSize = Long.parseLong(
output.firstMatch("reducing class space size from " + maxClassSpaceSize + " to (\\d+)", 1));
if (reducedSize < (maxClassSpaceSize - maxExpectedArchiveSize)) {
output.reportDiagnosticSummary();
throw new RuntimeException("Class space size too small?");
}
output.shouldMatch("Compressed class space.*" + reducedSize);
}
break;
default:
throw new RuntimeException("invalid sub test " + args[0]);
}
}
}

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