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8328168: Epsilon: Premature OOM when allocating object larger than un…
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…committed heap size

Backport-of: 7baec6622254fc21e315b974a213605a7605daac
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shipilev committed Apr 29, 2024
1 parent 71d0fcf commit 0f4bc65
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Showing 2 changed files with 51 additions and 4 deletions.
12 changes: 8 additions & 4 deletions src/hotspot/share/gc/epsilon/epsilonHeap.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -125,17 +125,21 @@ HeapWord* EpsilonHeap::allocate_work(size_t size, bool verbose) {

// Expand and loop back if space is available
size_t size_in_bytes = size * HeapWordSize;
size_t space_left = max_capacity() - capacity();
size_t uncommitted_space = max_capacity() - capacity();
size_t unused_space = max_capacity() - used();
size_t want_space = MAX2(size_in_bytes, EpsilonMinHeapExpand);
assert(unused_space >= uncommitted_space,
"Unused (" SIZE_FORMAT ") >= uncommitted (" SIZE_FORMAT ")",
unused_space, uncommitted_space);

if (want_space < space_left) {
if (want_space < uncommitted_space) {
// Enough space to expand in bulk:
bool expand = _virtual_space.expand_by(want_space);
assert(expand, "Should be able to expand");
} else if (size_in_bytes < space_left) {
} else if (size_in_bytes < unused_space) {
// No space to expand in bulk, and this allocation is still possible,
// take all the remaining space:
bool expand = _virtual_space.expand_by(space_left);
bool expand = _virtual_space.expand_by(uncommitted_space);
assert(expand, "Should be able to expand");
} else {
// No space left:
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43 changes: 43 additions & 0 deletions test/hotspot/jtreg/gc/epsilon/TestEnoughUnusedSpace.java
Original file line number Diff line number Diff line change
@@ -0,0 +1,43 @@
/*
* Copyright (c) 2024, 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.
*
*/

package gc.epsilon;

/**
* @test TestEnoughUnusedSpace
* @requires vm.gc.Epsilon
* @summary Epsilon should allocates object successfully if it has enough space.
* @run main/othervm -Xms64M -Xmx128M -XX:+UnlockExperimentalVMOptions
* -XX:+UseEpsilonGC gc.epsilon.TestEnoughUnusedSpace
*/

public class TestEnoughUnusedSpace {
static volatile Object arr;

public static void main(String[] args) {
// Create an array about 90M. It should be created successfully
// instead of throwing OOME, because 90M is smaller than 128M.
arr = new byte[90 * 1024 * 1024];
}
}

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