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8306841: Generational ZGC: NMT reports Java heap size larger than max…
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… heap size

Reviewed-by: eosterlund, stuefe
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stefank committed Jun 8, 2023
1 parent ac3ce2b commit bb377b2
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Showing 2 changed files with 110 additions and 24 deletions.
51 changes: 27 additions & 24 deletions src/hotspot/share/gc/z/zPhysicalMemory.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -276,6 +276,13 @@ void ZPhysicalMemoryManager::try_enable_uncommit(size_t min_capacity, size_t max
}

void ZPhysicalMemoryManager::nmt_commit(zoffset offset, size_t size) const {
// NMT expects a 1-to-1 mapping between virtual and physical memory.
// ZGC can temporarily have multiple virtual addresses pointing to
// the same physical memory.
//
// When this function is called we don't know where in the virtual memory
// this physical memory will be mapped. So we fake that the virtual memory
// address is the heap base + the given offset.
const zaddress addr = ZOffset::address(offset);
MemTracker::record_virtual_memory_commit((void*)untype(addr), size, CALLER_PC);
}
Expand Down Expand Up @@ -320,6 +327,11 @@ bool ZPhysicalMemoryManager::commit(ZPhysicalMemory& pmem) {

// Commit segment
const size_t committed = _backing.commit(segment.start(), segment.size());

// Register with NMT
nmt_commit(segment.start(), committed);

// Register committed segment
if (!pmem.commit_segment(i, committed)) {
// Failed or partially failed
return false;
Expand All @@ -341,6 +353,11 @@ bool ZPhysicalMemoryManager::uncommit(ZPhysicalMemory& pmem) {

// Uncommit segment
const size_t uncommitted = _backing.uncommit(segment.start(), segment.size());

// Unregister with NMT
nmt_uncommit(segment.start(), uncommitted);

// Deregister uncommitted segment
if (!pmem.uncommit_segment(i, uncommitted)) {
// Failed or partially failed
return false;
Expand All @@ -351,12 +368,16 @@ bool ZPhysicalMemoryManager::uncommit(ZPhysicalMemory& pmem) {
return true;
}

void ZPhysicalMemoryManager::pretouch_view(zaddress addr, size_t size) const {
void ZPhysicalMemoryManager::pretouch(zoffset offset, size_t size) const {
const uintptr_t addr = untype(ZOffset::address(offset));
const size_t page_size = ZLargePages::is_explicit() ? ZGranuleSize : os::vm_page_size();
os::pretouch_memory((void*)untype(addr), (void*)(untype(addr) + size), page_size);
os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
}

void ZPhysicalMemoryManager::map_view(zaddress_unsafe addr, const ZPhysicalMemory& pmem) const {
// Map virtual memory to physcial memory
void ZPhysicalMemoryManager::map(zoffset offset, const ZPhysicalMemory& pmem) const {
const zaddress_unsafe addr = ZOffset::address_unsafe(offset);

size_t size = 0;

// Map segments
Expand All @@ -375,27 +396,9 @@ void ZPhysicalMemoryManager::map_view(zaddress_unsafe addr, const ZPhysicalMemor
}
}

void ZPhysicalMemoryManager::unmap_view(zaddress_unsafe addr, size_t size) const {
_backing.unmap(addr, size);
}

void ZPhysicalMemoryManager::pretouch(zoffset offset, size_t size) const {
// Pre-touch all views
pretouch_view(ZOffset::address(offset), size);
}

void ZPhysicalMemoryManager::map(zoffset offset, const ZPhysicalMemory& pmem) const {
const size_t size = pmem.size();

// Map all views
map_view(ZOffset::address_unsafe(offset), pmem);

nmt_commit(offset, size);
}

// Unmap virtual memory from physical memory
void ZPhysicalMemoryManager::unmap(zoffset offset, size_t size) const {
nmt_uncommit(offset, size);
const zaddress_unsafe addr = ZOffset::address_unsafe(offset);

// Unmap all views
unmap_view(ZOffset::address_unsafe(offset), size);
_backing.unmap(addr, size);
}
83 changes: 83 additions & 0 deletions test/hotspot/jtreg/runtime/NMT/NMTJavaHeapTest.java
Original file line number Diff line number Diff line change
@@ -0,0 +1,83 @@
/*
* Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

/*
* @test
* @bug 8306841
* @summary Sanity check Java Heap size values
* @modules java.base/jdk.internal.misc
* @library /test/lib
* @run driver NMTJavaHeapTest
*/

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

public class NMTJavaHeapTest {
public static void main(String args[]) throws Exception {
ProcessBuilder pb = ProcessTools.createTestJvm(
"-XX:+UnlockDiagnosticVMOptions",
"-XX:+PrintNMTStatistics",
"-XX:NativeMemoryTracking=summary",
"-version");

OutputAnalyzer output = new OutputAnalyzer(pb.start());

// Java Heap (reserved=786432KB, committed=49152KB)
String pattern = ".*Java Heap \\(reserved=.*, committed=(.*)\\).*";
String committed = output.firstMatch(pattern, 1);
Asserts.assertNotNull(committed, "Couldn't find pattern '" + pattern
+ "': in output '" + output.getOutput() + "'");

long committedBytes = committedStringToBytes(committed);

// Must be more than zero
Asserts.assertGT(committedBytes, 0L);

// Compare against the max heap size
long maxBytes = Runtime.getRuntime().maxMemory();
Asserts.assertLTE(committedBytes, maxBytes);
}

private static long K = 1024;
private static long M = K * 1024;
private static long G = M * 1024;

private static long committedStringToBytes(String committed) {
long multiplier = 1;
if (committed.endsWith("GB")) {
multiplier = G;
committed = committed.replace("GB", "");
} else if (committed.endsWith("MB")) {
multiplier = M;
committed = committed.replace("MB", "");
} else if (committed.endsWith("KB")) {
multiplier = K;
committed = committed.replace("KB", "");
}

return Long.parseLong(committed) * multiplier;
}
}

3 comments on commit bb377b2

@openjdk-notifier
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@JesperIRL
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/tag jdk-22+0

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@openjdk openjdk bot commented on bb377b2 Jun 8, 2023

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@JesperIRL The tag jdk-22+0 was successfully created.

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