Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * 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/thread.inline.hpp"

 #include "runtime/threadLocalStorage.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 BsdThreads 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 Bsd 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

 }