1 /* 2 * Copyright (c) 1999, 2003, 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 25 #include "incls/_precompiled.incl" 26 #include "incls/_threadLS_linux_x86.cpp.incl" 27 28 // Map stack pointer (%esp) to thread pointer for faster TLS access 29 // 30 // Here we use a flat table for better performance. Getting current thread 31 // is down to one memory access (read _sp_map[%esp>>12]) in generated code 32 // and two in runtime code (-fPIC code needs an extra load for _sp_map). 33 // 34 // This code assumes stack page is not shared by different threads. It works 35 // in 32-bit VM when page size is 4K (or a multiple of 4K, if that matters). 36 // 37 // Notice that _sp_map is allocated in the bss segment, which is ZFOD 38 // (zero-fill-on-demand). While it reserves 4M address space upfront, 39 // actual memory pages are committed on demand. 40 // 41 // If an application creates and destroys a lot of threads, usually the 42 // stack space freed by a thread will soon get reused by new thread 43 // (this is especially true in NPTL or LinuxThreads in fixed-stack mode). 44 // No memory page in _sp_map is wasted. 45 // 46 // However, it's still possible that we might end up populating & | 1 /* 2 * Copyright (c) 1999, 2010, 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 25 #include "precompiled.hpp" 26 #include "runtime/threadLocalStorage.hpp" 27 #include "thread_linux.inline.hpp" 28 29 // Map stack pointer (%esp) to thread pointer for faster TLS access 30 // 31 // Here we use a flat table for better performance. Getting current thread 32 // is down to one memory access (read _sp_map[%esp>>12]) in generated code 33 // and two in runtime code (-fPIC code needs an extra load for _sp_map). 34 // 35 // This code assumes stack page is not shared by different threads. It works 36 // in 32-bit VM when page size is 4K (or a multiple of 4K, if that matters). 37 // 38 // Notice that _sp_map is allocated in the bss segment, which is ZFOD 39 // (zero-fill-on-demand). While it reserves 4M address space upfront, 40 // actual memory pages are committed on demand. 41 // 42 // If an application creates and destroys a lot of threads, usually the 43 // stack space freed by a thread will soon get reused by new thread 44 // (this is especially true in NPTL or LinuxThreads in fixed-stack mode). 45 // No memory page in _sp_map is wasted. 46 // 47 // However, it's still possible that we might end up populating & |