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/*
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* Copyright (c) 2019, Oracle and/or its affiliates. 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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#include "precompiled.hpp"
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#include "gc/z/zCPU.inline.hpp"
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#include "gc/z/zGlobals.hpp"
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#include "gc/z/zHeuristics.hpp"
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#include "gc/z/zUtils.inline.hpp"
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#include "logging/log.hpp"
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#include "runtime/globals.hpp"
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#include "runtime/os.hpp"
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void ZHeuristics::set_medium_page_size() {
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// Set ZPageSizeMedium so that a medium page occupies at most 3.125% of the
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// max heap size. ZPageSizeMedium is initially set to 0, which means medium
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// pages are effectively disabled. It is adjusted only if ZPageSizeMedium
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// becomes larger than ZPageSizeSmall.
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const size_t min = ZGranuleSize;
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const size_t max = ZGranuleSize * 16;
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const size_t unclamped = MaxHeapSize * 0.03125;
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const size_t clamped = MIN2(MAX2(min, unclamped), max);
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const size_t size = ZUtils::round_down_power_of_2(clamped);
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if (size > ZPageSizeSmall) {
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// Enable medium pages
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ZPageSizeMedium = size;
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ZPageSizeMediumShift = log2_intptr(ZPageSizeMedium);
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ZObjectSizeLimitMedium = ZPageSizeMedium / 8;
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ZObjectAlignmentMediumShift = ZPageSizeMediumShift - 13;
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ZObjectAlignmentMedium = 1 << ZObjectAlignmentMediumShift;
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log_info(gc, init)("Medium Page Size: " SIZE_FORMAT "M", ZPageSizeMedium / M);
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} else {
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log_info(gc, init)("Medium Page Size: N/A");
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}
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}
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bool ZHeuristics::use_per_cpu_shared_small_pages() {
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// Use per-CPU shared small pages only if these pages occupy at most 3.125%
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// of the max heap size. Otherwise fall back to using a single shared small
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// page. This is useful when using small heaps on large machines.
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const size_t per_cpu_share = (MaxHeapSize * 0.03125) / ZCPU::count();
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return per_cpu_share >= ZPageSizeSmall;
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}
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