Mercurial > hg > graal-jvmci-8

comparison src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp @ 0:a61af66fc99e jdk7-b24

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children c18cbe5936b8
comparison
equal deleted inserted replaced
-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 1999-2003 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any 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 &
47 // committing a large fraction of the 4M table over time, but the actual
48 // amount of live data in the table could be quite small. The max wastage
49 // is less than 4M bytes. If it becomes an issue, we could use madvise()
50 // with MADV_DONTNEED to reclaim unused (i.e. all-zero) pages in _sp_map.
51 // MADV_DONTNEED on Linux keeps the virtual memory mapping, but zaps the
52 // physical memory page (i.e. similar to MADV_FREE on Solaris).
53
54 #ifndef AMD64
55 Thread* ThreadLocalStorage::_sp_map[1UL << (SP_BITLENGTH - PAGE_SHIFT)];
56 #endif // !AMD64
57
58 void ThreadLocalStorage::generate_code_for_get_thread() {
59 // nothing we can do here for user-level thread
60 }
61
62 void ThreadLocalStorage::pd_init() {
63 #ifndef AMD64
64 assert(align_size_down(os::vm_page_size(), PAGE_SIZE) == os::vm_page_size(),
65 "page size must be multiple of PAGE_SIZE");
66 #endif // !AMD64
67 }
68
69 void ThreadLocalStorage::pd_set_thread(Thread* thread) {
70 os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
71
72 #ifndef AMD64
73 address stack_top = os::current_stack_base();
74 size_t stack_size = os::current_stack_size();
75
76 for (address p = stack_top - stack_size; p < stack_top; p += PAGE_SIZE) {
77 // pd_set_thread() is called with non-NULL value when a new thread is
78 // created/attached, or with NULL value when a thread is about to exit.
79 // If both "thread" and the corresponding _sp_map[] entry are non-NULL,
80 // they should have the same value. Otherwise it might indicate that the
81 // stack page is shared by multiple threads. However, a more likely cause
82 // for this assertion to fail is that an attached thread exited without
83 // detaching itself from VM, which is a program error and could cause VM
84 // to crash.
85 assert(thread == NULL || _sp_map[(uintptr_t)p >> PAGE_SHIFT] == NULL ||
86 thread == _sp_map[(uintptr_t)p >> PAGE_SHIFT],
87 "thread exited without detaching from VM??");
88 _sp_map[(uintptr_t)p >> PAGE_SHIFT] = thread;
89 }
90 #endif // !AMD64
91 }