diff --git a/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp b/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp index c0d6b007a27..72a3f411ea0 100644 --- a/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp +++ b/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp @@ -154,7 +154,7 @@ HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, Shenandoah HeapWord* result = nullptr; size_t size = req.size(); - if (ShenandoahElasticTLAB && req.is_lab_alloc()) { + if (req.is_lab_alloc()) { size_t free = align_down(r->free() >> LogHeapWordSize, MinObjAlignment); if (size > free) { size = free; diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp index 3426aba9d94..586056c0e30 100644 --- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp @@ -1186,13 +1186,9 @@ void ShenandoahHeap::gclabs_retire(bool resize) { // Returns size in bytes size_t ShenandoahHeap::unsafe_max_tlab_alloc(Thread *thread) const { - if (ShenandoahElasticTLAB) { - // With Elastic TLABs, return the max allowed size, and let the allocation path - // figure out the safe size for current allocation. - return ShenandoahHeapRegion::max_tlab_size_bytes(); - } else { - return MIN2(_free_set->unsafe_peek_free(), ShenandoahHeapRegion::max_tlab_size_bytes()); - } + // Return the max allowed size, and let the allocation path + // figure out the safe size for current allocation. + return ShenandoahHeapRegion::max_tlab_size_bytes(); } size_t ShenandoahHeap::max_tlab_size() const { diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp index 6cac61f848a..a46c7edc348 100644 --- a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp +++ b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp @@ -607,26 +607,8 @@ size_t ShenandoahHeapRegion::setup_sizes(size_t max_heap_size) { HumongousThresholdBytes = HumongousThresholdWords * HeapWordSize; assert (HumongousThresholdBytes <= RegionSizeBytes, "sanity"); - // The rationale for trimming the TLAB sizes has to do with the raciness in - // TLAB allocation machinery. It may happen that TLAB sizing policy polls Shenandoah - // about next free size, gets the answer for region #N, goes away for a while, then - // tries to allocate in region #N, and fail because some other thread have claimed part - // of the region #N, and then the freeset allocation code has to retire the region #N, - // before moving the allocation to region #N+1. - // - // The worst case realizes when "answer" is "region size", which means it could - // prematurely retire an entire region. Having smaller TLABs does not fix that - // completely, but reduces the probability of too wasteful region retirement. - // With current divisor, we will waste no more than 1/8 of region size in the worst - // case. This also has a secondary effect on collection set selection: even under - // the race, the regions would be at least 7/8 used, which allows relying on - // "used" - "live" for cset selection. Otherwise, we can get the fragmented region - // below the garbage threshold that would never be considered for collection. - // - // The whole thing is mitigated if Elastic TLABs are enabled. - // guarantee(MaxTLABSizeWords == 0, "we should only set it once"); - MaxTLABSizeWords = MIN2(ShenandoahElasticTLAB ? RegionSizeWords : (RegionSizeWords / 8), HumongousThresholdWords); + MaxTLABSizeWords = MIN2(RegionSizeWords, HumongousThresholdWords); MaxTLABSizeWords = align_down(MaxTLABSizeWords, MinObjAlignment); guarantee(MaxTLABSizeBytes == 0, "we should only set it once"); diff --git a/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp b/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp index 1b622946cba..fae08c1e418 100644 --- a/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp +++ b/src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp @@ -215,9 +215,6 @@ " 3 = previous level, plus all reachable objects; " \ " 4 = previous level, plus all marked objects") \ \ - product(bool, ShenandoahElasticTLAB, true, DIAGNOSTIC, \ - "Use Elastic TLABs with Shenandoah") \ - \ product(uintx, ShenandoahEvacReserve, 5, EXPERIMENTAL, \ "How much of heap to reserve for evacuations. Larger values make "\ "GC evacuate more live objects on every cycle, while leaving " \ diff --git a/test/hotspot/jtreg/gc/shenandoah/TestElasticTLAB.java b/test/hotspot/jtreg/gc/shenandoah/TestElasticTLAB.java deleted file mode 100644 index b498228a932..00000000000 --- a/test/hotspot/jtreg/gc/shenandoah/TestElasticTLAB.java +++ /dev/null @@ -1,62 +0,0 @@ -/* - * Copyright (c) 2018, Red Hat, Inc. 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 - * @key randomness - * @summary Test that Shenandoah is able to work with elastic TLABs - * @requires vm.gc.Shenandoah - * @library /test/lib - * - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:-ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:-ShenandoahElasticTLAB TestElasticTLAB - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:+ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:-UseTLAB -XX:+ShenandoahElasticTLAB TestElasticTLAB - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:-ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:-ShenandoahElasticTLAB TestElasticTLAB - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:+ShenandoahElasticTLAB -XX:+ShenandoahVerify TestElasticTLAB - * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -Xmx1g -XX:+UseTLAB -XX:+ShenandoahElasticTLAB TestElasticTLAB - */ - -import java.util.Random; -import jdk.test.lib.Utils; - -public class TestElasticTLAB { - - static final long TARGET_MB = Long.getLong("target", 10_000); // 10 Gb allocation - - static volatile Object sink; - - public static void main(String[] args) throws Exception { - final int min = 0; - final int max = 384 * 1024; - long count = TARGET_MB * 1024 * 1024 / (16 + 4 * (min + (max - min) / 2)); - - Random r = Utils.getRandomInstance(); - for (long c = 0; c < count; c++) { - sink = new int[min + r.nextInt(max - min)]; - } - } - -}