1 /* 2 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 24 #include "precompiled.hpp" 25 #include "gc/z/zCPU.inline.hpp" 26 #include "gc/z/zGlobals.hpp" 27 #include "gc/z/zHeuristics.hpp" 28 #include "gc/z/zUtils.inline.hpp" 29 #include "logging/log.hpp" 30 #include "runtime/globals.hpp" 31 #include "runtime/os.hpp" 32 33 void ZHeuristics::set_medium_page_size() { 34 // Set ZPageSizeMedium so that a medium page occupies at most 3.125% of the 35 // max heap size. ZPageSizeMedium is initially set to 0, which means medium 36 // pages are effectively disabled. It is adjusted only if ZPageSizeMedium 37 // becomes larger than ZPageSizeSmall. 38 const size_t min = ZGranuleSize; 39 const size_t max = ZGranuleSize * 16; 40 const size_t unclamped = MaxHeapSize * 0.03125; 41 const size_t clamped = MIN2(MAX2(min, unclamped), max); 42 const size_t size = ZUtils::round_down_power_of_2(clamped); 43 44 if (size > ZPageSizeSmall) { 45 // Enable medium pages 46 ZPageSizeMedium = size; 47 ZPageSizeMediumShift = log2_intptr(ZPageSizeMedium); 48 ZObjectSizeLimitMedium = ZPageSizeMedium / 8; 49 ZObjectAlignmentMediumShift = ZPageSizeMediumShift - 13; 50 ZObjectAlignmentMedium = 1 << ZObjectAlignmentMediumShift; 51 52 log_info(gc, init)("Medium Page Size: " SIZE_FORMAT "M", ZPageSizeMedium / M); 53 } else { 54 log_info(gc, init)("Medium Page Size: N/A"); 55 } 56 } 57 58 bool ZHeuristics::per_cpu_shared_small_page() { 59 // Use per-CPU shared small pages only if these pages occupy at most 3.125% 60 // of the max heap size. Otherwise fall back to using a single shared small 61 // page. This is useful when using small heaps on large machines. 62 const size_t per_cpu_share = (MaxHeapSize * 0.03125) / ZCPU::count(); 63 return per_cpu_share >= ZPageSizeSmall; 64 }