Mercurial > hg > graal-compiler
view src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp @ 2818:bf12196e2a60
Made null checks floating.
author | Thomas Wuerthinger <thomas@wuerthinger.net> |
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date | Mon, 30 May 2011 15:36:06 +0200 |
parents | f95d63e2154a |
children | 65dba8692db7 |
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/* * Copyright (c) 1999, 2010, Oracle and/or its affiliates. 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. * */ #include "precompiled.hpp" #include "runtime/threadLocalStorage.hpp" #include "thread_linux.inline.hpp" // Map stack pointer (%esp) to thread pointer for faster TLS access // // Here we use a flat table for better performance. Getting current thread // is down to one memory access (read _sp_map[%esp>>12]) in generated code // and two in runtime code (-fPIC code needs an extra load for _sp_map). // // This code assumes stack page is not shared by different threads. It works // in 32-bit VM when page size is 4K (or a multiple of 4K, if that matters). // // Notice that _sp_map is allocated in the bss segment, which is ZFOD // (zero-fill-on-demand). While it reserves 4M address space upfront, // actual memory pages are committed on demand. // // If an application creates and destroys a lot of threads, usually the // stack space freed by a thread will soon get reused by new thread // (this is especially true in NPTL or LinuxThreads in fixed-stack mode). // No memory page in _sp_map is wasted. // // However, it's still possible that we might end up populating & // committing a large fraction of the 4M table over time, but the actual // amount of live data in the table could be quite small. The max wastage // is less than 4M bytes. If it becomes an issue, we could use madvise() // with MADV_DONTNEED to reclaim unused (i.e. all-zero) pages in _sp_map. // MADV_DONTNEED on Linux keeps the virtual memory mapping, but zaps the // physical memory page (i.e. similar to MADV_FREE on Solaris). #ifndef AMD64 Thread* ThreadLocalStorage::_sp_map[1UL << (SP_BITLENGTH - PAGE_SHIFT)]; #endif // !AMD64 void ThreadLocalStorage::generate_code_for_get_thread() { // nothing we can do here for user-level thread } void ThreadLocalStorage::pd_init() { #ifndef AMD64 assert(align_size_down(os::vm_page_size(), PAGE_SIZE) == os::vm_page_size(), "page size must be multiple of PAGE_SIZE"); #endif // !AMD64 } void ThreadLocalStorage::pd_set_thread(Thread* thread) { os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread); #ifndef AMD64 address stack_top = os::current_stack_base(); size_t stack_size = os::current_stack_size(); for (address p = stack_top - stack_size; p < stack_top; p += PAGE_SIZE) { // pd_set_thread() is called with non-NULL value when a new thread is // created/attached, or with NULL value when a thread is about to exit. // If both "thread" and the corresponding _sp_map[] entry are non-NULL, // they should have the same value. Otherwise it might indicate that the // stack page is shared by multiple threads. However, a more likely cause // for this assertion to fail is that an attached thread exited without // detaching itself from VM, which is a program error and could cause VM // to crash. assert(thread == NULL || _sp_map[(uintptr_t)p >> PAGE_SHIFT] == NULL || thread == _sp_map[(uintptr_t)p >> PAGE_SHIFT], "thread exited without detaching from VM??"); _sp_map[(uintptr_t)p >> PAGE_SHIFT] = thread; } #endif // !AMD64 }