8321120: Shenandoah: Remove ShenandoahElasticTLAB flag
Reviewed-by: kdnilsen, ysr
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parent
9b8eaa2fc3
commit
93b9235f19
src/hotspot/share/gc/shenandoah
test/hotspot/jtreg/gc/shenandoah
@ -154,7 +154,7 @@ HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, Shenandoah
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HeapWord* result = nullptr;
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size_t size = req.size();
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if (ShenandoahElasticTLAB && req.is_lab_alloc()) {
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if (req.is_lab_alloc()) {
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size_t free = align_down(r->free() >> LogHeapWordSize, MinObjAlignment);
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if (size > free) {
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size = free;
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@ -1186,13 +1186,9 @@ void ShenandoahHeap::gclabs_retire(bool resize) {
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// Returns size in bytes
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size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const {
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if (ShenandoahElasticTLAB) {
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// With Elastic TLABs, return the max allowed size, and let the allocation path
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// figure out the safe size for current allocation.
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return ShenandoahHeapRegion::max_tlab_size_bytes();
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} else {
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return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes());
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}
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// Return the max allowed size, and let the allocation path
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// figure out the safe size for current allocation.
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return ShenandoahHeapRegion::max_tlab_size_bytes();
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}
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size_t ShenandoahHeap::max_tlab_size() const {
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@ -607,26 +607,8 @@ size_t ShenandoahHeapRegion::setup_sizes(size_t max_heap_size) {
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HumongousThresholdBytes = HumongousThresholdWords * HeapWordSize;
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assert (HumongousThresholdBytes <= RegionSizeBytes, "sanity");
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// The rationale for trimming the TLAB sizes has to do with the raciness in
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// TLAB allocation machinery. It may happen that TLAB sizing policy polls Shenandoah
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// about next free size, gets the answer for region #N, goes away for a while, then
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// tries to allocate in region #N, and fail because some other thread have claimed part
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// of the region #N, and then the freeset allocation code has to retire the region #N,
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// before moving the allocation to region #N+1.
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//
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// The worst case realizes when "answer" is "region size", which means it could
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// prematurely retire an entire region. Having smaller TLABs does not fix that
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// completely, but reduces the probability of too wasteful region retirement.
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// With current divisor, we will waste no more than 1/8 of region size in the worst
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// case. This also has a secondary effect on collection set selection: even under
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// the race, the regions would be at least 7/8 used, which allows relying on
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// "used" - "live" for cset selection. Otherwise, we can get the fragmented region
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// below the garbage threshold that would never be considered for collection.
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//
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// The whole thing is mitigated if Elastic TLABs are enabled.
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//
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guarantee(MaxTLABSizeWords == 0, "we should only set it once");
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MaxTLABSizeWords = MIN2(ShenandoahElasticTLAB ? RegionSizeWords : (RegionSizeWords / 8), HumongousThresholdWords);
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MaxTLABSizeWords = MIN2(RegionSizeWords, HumongousThresholdWords);
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MaxTLABSizeWords = align_down(MaxTLABSizeWords, MinObjAlignment);
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guarantee(MaxTLABSizeBytes == 0, "we should only set it once");
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@ -215,9 +215,6 @@
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" 3 = previous level, plus all reachable objects; " \
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" 4 = previous level, plus all marked objects") \
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\
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product(bool, ShenandoahElasticTLAB, true, DIAGNOSTIC, \
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"Use Elastic TLABs with Shenandoah") \
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\
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product(uintx, ShenandoahEvacReserve, 5, EXPERIMENTAL, \
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"How much of heap to reserve for evacuations. Larger values make "\
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"GC evacuate more live objects on every cycle, while leaving " \
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@ -1,62 +0,0 @@
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/*
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* Copyright (c) 2018, Red Hat, Inc. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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/*
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* @test
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* @key randomness
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* @summary Test that Shenandoah is able to work with elastic TLABs
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* @requires vm.gc.Shenandoah
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* @library /test/lib
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*
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:-ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:-ShenandoahElasticTLAB TestElasticTLAB
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:+ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:+ShenandoahElasticTLAB TestElasticTLAB
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:-ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:-ShenandoahElasticTLAB TestElasticTLAB
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:+ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB
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* @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:+ShenandoahElasticTLAB TestElasticTLAB
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*/
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import java.util.Random;
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import jdk.test.lib.Utils;
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public class TestElasticTLAB {
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static final long TARGET_MB = Long.getLong("target", 10_000); // 10 Gb allocation
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static volatile Object sink;
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public static void main(String[] args) throws Exception {
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final int min = 0;
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final int max = 384 * 1024;
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long count = TARGET_MB * 1024 * 1024 / (16 + 4 * (min + (max - min) / 2));
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Random r = Utils.getRandomInstance();
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for (long c = 0; c < count; c++) {
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sink = new int[min + r.nextInt(max - min)];
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}
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}
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}
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