1 /*
   2  * Copyright (c) 1997, 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 "incls/_precompiled.incl"
  26 # include "incls/_os.cpp.incl"
  27 
  28 # include <signal.h>
  29 
  30 OSThread*         os::_starting_thread    = NULL;
  31 address           os::_polling_page       = NULL;
  32 volatile int32_t* os::_mem_serialize_page = NULL;
  33 uintptr_t         os::_serialize_page_mask = 0;
  34 long              os::_rand_seed          = 1;
  35 int               os::_processor_count    = 0;
  36 size_t            os::_page_sizes[os::page_sizes_max];
  37 
  38 #ifndef PRODUCT
  39 int os::num_mallocs = 0;            // # of calls to malloc/realloc
  40 size_t os::alloc_bytes = 0;         // # of bytes allocated
  41 int os::num_frees = 0;              // # of calls to free
  42 #endif
  43 
  44 // Fill in buffer with current local time as an ISO-8601 string.
  45 // E.g., yyyy-mm-ddThh:mm:ss-zzzz.
  46 // Returns buffer, or NULL if it failed.
  47 // This would mostly be a call to
  48 //     strftime(...., "%Y-%m-%d" "T" "%H:%M:%S" "%z", ....)
  49 // except that on Windows the %z behaves badly, so we do it ourselves.
  50 // Also, people wanted milliseconds on there,
  51 // and strftime doesn't do milliseconds.
  52 char* os::iso8601_time(char* buffer, size_t buffer_length) {
  53   // Output will be of the form "YYYY-MM-DDThh:mm:ss.mmm+zzzz\0"
  54   //                                      1         2
  55   //                             12345678901234567890123456789
  56   static const char* iso8601_format =
  57     "%04d-%02d-%02dT%02d:%02d:%02d.%03d%c%02d%02d";
  58   static const size_t needed_buffer = 29;
  59 
  60   // Sanity check the arguments
  61   if (buffer == NULL) {
  62     assert(false, "NULL buffer");
  63     return NULL;
  64   }
  65   if (buffer_length < needed_buffer) {
  66     assert(false, "buffer_length too small");
  67     return NULL;
  68   }
  69   // Get the current time
  70   jlong milliseconds_since_19700101 = javaTimeMillis();
  71   const int milliseconds_per_microsecond = 1000;
  72   const time_t seconds_since_19700101 =
  73     milliseconds_since_19700101 / milliseconds_per_microsecond;
  74   const int milliseconds_after_second =
  75     milliseconds_since_19700101 % milliseconds_per_microsecond;
  76   // Convert the time value to a tm and timezone variable
  77   struct tm time_struct;
  78   if (localtime_pd(&seconds_since_19700101, &time_struct) == NULL) {
  79     assert(false, "Failed localtime_pd");
  80     return NULL;
  81   }
  82   const time_t zone = timezone;
  83 
  84   // If daylight savings time is in effect,
  85   // we are 1 hour East of our time zone
  86   const time_t seconds_per_minute = 60;
  87   const time_t minutes_per_hour = 60;
  88   const time_t seconds_per_hour = seconds_per_minute * minutes_per_hour;
  89   time_t UTC_to_local = zone;
  90   if (time_struct.tm_isdst > 0) {
  91     UTC_to_local = UTC_to_local - seconds_per_hour;
  92   }
  93   // Compute the time zone offset.
  94   //    localtime_pd() sets timezone to the difference (in seconds)
  95   //    between UTC and and local time.
  96   //    ISO 8601 says we need the difference between local time and UTC,
  97   //    we change the sign of the localtime_pd() result.
  98   const time_t local_to_UTC = -(UTC_to_local);
  99   // Then we have to figure out if if we are ahead (+) or behind (-) UTC.
 100   char sign_local_to_UTC = '+';
 101   time_t abs_local_to_UTC = local_to_UTC;
 102   if (local_to_UTC < 0) {
 103     sign_local_to_UTC = '-';
 104     abs_local_to_UTC = -(abs_local_to_UTC);
 105   }
 106   // Convert time zone offset seconds to hours and minutes.
 107   const time_t zone_hours = (abs_local_to_UTC / seconds_per_hour);
 108   const time_t zone_min =
 109     ((abs_local_to_UTC % seconds_per_hour) / seconds_per_minute);
 110 
 111   // Print an ISO 8601 date and time stamp into the buffer
 112   const int year = 1900 + time_struct.tm_year;
 113   const int month = 1 + time_struct.tm_mon;
 114   const int printed = jio_snprintf(buffer, buffer_length, iso8601_format,
 115                                    year,
 116                                    month,
 117                                    time_struct.tm_mday,
 118                                    time_struct.tm_hour,
 119                                    time_struct.tm_min,
 120                                    time_struct.tm_sec,
 121                                    milliseconds_after_second,
 122                                    sign_local_to_UTC,
 123                                    zone_hours,
 124                                    zone_min);
 125   if (printed == 0) {
 126     assert(false, "Failed jio_printf");
 127     return NULL;
 128   }
 129   return buffer;
 130 }
 131 
 132 OSReturn os::set_priority(Thread* thread, ThreadPriority p) {
 133 #ifdef ASSERT
 134   if (!(!thread->is_Java_thread() ||
 135          Thread::current() == thread  ||
 136          Threads_lock->owned_by_self()
 137          || thread->is_Compiler_thread()
 138         )) {
 139     assert(false, "possibility of dangling Thread pointer");
 140   }
 141 #endif
 142 
 143   if (p >= MinPriority && p <= MaxPriority) {
 144     int priority = java_to_os_priority[p];
 145     return set_native_priority(thread, priority);
 146   } else {
 147     assert(false, "Should not happen");
 148     return OS_ERR;
 149   }
 150 }
 151 
 152 
 153 OSReturn os::get_priority(const Thread* const thread, ThreadPriority& priority) {
 154   int p;
 155   int os_prio;
 156   OSReturn ret = get_native_priority(thread, &os_prio);
 157   if (ret != OS_OK) return ret;
 158 
 159   for (p = MaxPriority; p > MinPriority && java_to_os_priority[p] > os_prio; p--) ;
 160   priority = (ThreadPriority)p;
 161   return OS_OK;
 162 }
 163 
 164 
 165 // --------------------- sun.misc.Signal (optional) ---------------------
 166 
 167 
 168 // SIGBREAK is sent by the keyboard to query the VM state
 169 #ifndef SIGBREAK
 170 #define SIGBREAK SIGQUIT
 171 #endif
 172 
 173 // sigexitnum_pd is a platform-specific special signal used for terminating the Signal thread.
 174 
 175 
 176 static void signal_thread_entry(JavaThread* thread, TRAPS) {
 177   os::set_priority(thread, NearMaxPriority);
 178   while (true) {
 179     int sig;
 180     {
 181       // FIXME : Currently we have not decieded what should be the status
 182       //         for this java thread blocked here. Once we decide about
 183       //         that we should fix this.
 184       sig = os::signal_wait();
 185     }
 186     if (sig == os::sigexitnum_pd()) {
 187        // Terminate the signal thread
 188        return;
 189     }
 190 
 191     switch (sig) {
 192       case SIGBREAK: {
 193         // Check if the signal is a trigger to start the Attach Listener - in that
 194         // case don't print stack traces.
 195         if (!DisableAttachMechanism && AttachListener::is_init_trigger()) {
 196           continue;
 197         }
 198         // Print stack traces
 199         // Any SIGBREAK operations added here should make sure to flush
 200         // the output stream (e.g. tty->flush()) after output.  See 4803766.
 201         // Each module also prints an extra carriage return after its output.
 202         VM_PrintThreads op;
 203         VMThread::execute(&op);
 204         VM_PrintJNI jni_op;
 205         VMThread::execute(&jni_op);
 206         VM_FindDeadlocks op1(tty);
 207         VMThread::execute(&op1);
 208         Universe::print_heap_at_SIGBREAK();
 209         if (PrintClassHistogram) {
 210           VM_GC_HeapInspection op1(gclog_or_tty, true /* force full GC before heap inspection */,
 211                                    true /* need_prologue */);
 212           VMThread::execute(&op1);
 213         }
 214         if (JvmtiExport::should_post_data_dump()) {
 215           JvmtiExport::post_data_dump();
 216         }
 217         break;
 218       }
 219       default: {
 220         // Dispatch the signal to java
 221         HandleMark hm(THREAD);
 222         klassOop k = SystemDictionary::resolve_or_null(vmSymbolHandles::sun_misc_Signal(), THREAD);
 223         KlassHandle klass (THREAD, k);
 224         if (klass.not_null()) {
 225           JavaValue result(T_VOID);
 226           JavaCallArguments args;
 227           args.push_int(sig);
 228           JavaCalls::call_static(
 229             &result,
 230             klass,
 231             vmSymbolHandles::dispatch_name(),
 232             vmSymbolHandles::int_void_signature(),
 233             &args,
 234             THREAD
 235           );
 236         }
 237         if (HAS_PENDING_EXCEPTION) {
 238           // tty is initialized early so we don't expect it to be null, but
 239           // if it is we can't risk doing an initialization that might
 240           // trigger additional out-of-memory conditions
 241           if (tty != NULL) {
 242             char klass_name[256];
 243             char tmp_sig_name[16];
 244             const char* sig_name = "UNKNOWN";
 245             instanceKlass::cast(PENDING_EXCEPTION->klass())->
 246               name()->as_klass_external_name(klass_name, 256);
 247             if (os::exception_name(sig, tmp_sig_name, 16) != NULL)
 248               sig_name = tmp_sig_name;
 249             warning("Exception %s occurred dispatching signal %s to handler"
 250                     "- the VM may need to be forcibly terminated",
 251                     klass_name, sig_name );
 252           }
 253           CLEAR_PENDING_EXCEPTION;
 254         }
 255       }
 256     }
 257   }
 258 }
 259 
 260 
 261 void os::signal_init() {
 262   if (!ReduceSignalUsage) {
 263     // Setup JavaThread for processing signals
 264     EXCEPTION_MARK;
 265     klassOop k = SystemDictionary::resolve_or_fail(vmSymbolHandles::java_lang_Thread(), true, CHECK);
 266     instanceKlassHandle klass (THREAD, k);
 267     instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
 268 
 269     const char thread_name[] = "Signal Dispatcher";
 270     Handle string = java_lang_String::create_from_str(thread_name, CHECK);
 271 
 272     // Initialize thread_oop to put it into the system threadGroup
 273     Handle thread_group (THREAD, Universe::system_thread_group());
 274     JavaValue result(T_VOID);
 275     JavaCalls::call_special(&result, thread_oop,
 276                            klass,
 277                            vmSymbolHandles::object_initializer_name(),
 278                            vmSymbolHandles::threadgroup_string_void_signature(),
 279                            thread_group,
 280                            string,
 281                            CHECK);
 282 
 283     KlassHandle group(THREAD, SystemDictionary::ThreadGroup_klass());
 284     JavaCalls::call_special(&result,
 285                             thread_group,
 286                             group,
 287                             vmSymbolHandles::add_method_name(),
 288                             vmSymbolHandles::thread_void_signature(),
 289                             thread_oop,         // ARG 1
 290                             CHECK);
 291 
 292     os::signal_init_pd();
 293 
 294     { MutexLocker mu(Threads_lock);
 295       JavaThread* signal_thread = new JavaThread(&signal_thread_entry);
 296 
 297       // At this point it may be possible that no osthread was created for the
 298       // JavaThread due to lack of memory. We would have to throw an exception
 299       // in that case. However, since this must work and we do not allow
 300       // exceptions anyway, check and abort if this fails.
 301       if (signal_thread == NULL || signal_thread->osthread() == NULL) {
 302         vm_exit_during_initialization("java.lang.OutOfMemoryError",
 303                                       "unable to create new native thread");
 304       }
 305 
 306       java_lang_Thread::set_thread(thread_oop(), signal_thread);
 307       java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
 308       java_lang_Thread::set_daemon(thread_oop());
 309 
 310       signal_thread->set_threadObj(thread_oop());
 311       Threads::add(signal_thread);
 312       Thread::start(signal_thread);
 313     }
 314     // Handle ^BREAK
 315     os::signal(SIGBREAK, os::user_handler());
 316   }
 317 }
 318 
 319 
 320 void os::terminate_signal_thread() {
 321   if (!ReduceSignalUsage)
 322     signal_notify(sigexitnum_pd());
 323 }
 324 
 325 
 326 // --------------------- loading libraries ---------------------
 327 
 328 typedef jint (JNICALL *JNI_OnLoad_t)(JavaVM *, void *);
 329 extern struct JavaVM_ main_vm;
 330 
 331 static void* _native_java_library = NULL;
 332 
 333 void* os::native_java_library() {
 334   if (_native_java_library == NULL) {
 335     char buffer[JVM_MAXPATHLEN];
 336     char ebuf[1024];
 337 
 338     // Try to load verify dll first. In 1.3 java dll depends on it and is not
 339     // always able to find it when the loading executable is outside the JDK.
 340     // In order to keep working with 1.2 we ignore any loading errors.
 341     dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(), "verify");
 342     dll_load(buffer, ebuf, sizeof(ebuf));
 343 
 344     // Load java dll
 345     dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(), "java");
 346     _native_java_library = dll_load(buffer, ebuf, sizeof(ebuf));
 347     if (_native_java_library == NULL) {
 348       vm_exit_during_initialization("Unable to load native library", ebuf);
 349     }
 350   }
 351   static jboolean onLoaded = JNI_FALSE;
 352   if (onLoaded) {
 353     // We may have to wait to fire OnLoad until TLS is initialized.
 354     if (ThreadLocalStorage::is_initialized()) {
 355       // The JNI_OnLoad handling is normally done by method load in
 356       // java.lang.ClassLoader$NativeLibrary, but the VM loads the base library
 357       // explicitly so we have to check for JNI_OnLoad as well
 358       const char *onLoadSymbols[] = JNI_ONLOAD_SYMBOLS;
 359       JNI_OnLoad_t JNI_OnLoad = CAST_TO_FN_PTR(
 360           JNI_OnLoad_t, dll_lookup(_native_java_library, onLoadSymbols[0]));
 361       if (JNI_OnLoad != NULL) {
 362         JavaThread* thread = JavaThread::current();
 363         ThreadToNativeFromVM ttn(thread);
 364         HandleMark hm(thread);
 365         jint ver = (*JNI_OnLoad)(&main_vm, NULL);
 366         onLoaded = JNI_TRUE;
 367         if (!Threads::is_supported_jni_version_including_1_1(ver)) {
 368           vm_exit_during_initialization("Unsupported JNI version");
 369         }
 370       }
 371     }
 372   }
 373   return _native_java_library;
 374 }
 375 
 376 // --------------------- heap allocation utilities ---------------------
 377 
 378 char *os::strdup(const char *str) {
 379   size_t size = strlen(str);
 380   char *dup_str = (char *)malloc(size + 1);
 381   if (dup_str == NULL) return NULL;
 382   strcpy(dup_str, str);
 383   return dup_str;
 384 }
 385 
 386 
 387 
 388 #ifdef ASSERT
 389 #define space_before             (MallocCushion + sizeof(double))
 390 #define space_after              MallocCushion
 391 #define size_addr_from_base(p)   (size_t*)(p + space_before - sizeof(size_t))
 392 #define size_addr_from_obj(p)    ((size_t*)p - 1)
 393 // MallocCushion: size of extra cushion allocated around objects with +UseMallocOnly
 394 // NB: cannot be debug variable, because these aren't set from the command line until
 395 // *after* the first few allocs already happened
 396 #define MallocCushion            16
 397 #else
 398 #define space_before             0
 399 #define space_after              0
 400 #define size_addr_from_base(p)   should not use w/o ASSERT
 401 #define size_addr_from_obj(p)    should not use w/o ASSERT
 402 #define MallocCushion            0
 403 #endif
 404 #define paranoid                 0  /* only set to 1 if you suspect checking code has bug */
 405 
 406 #ifdef ASSERT
 407 inline size_t get_size(void* obj) {
 408   size_t size = *size_addr_from_obj(obj);
 409   if (size < 0) {
 410     fatal(err_msg("free: size field of object #" PTR_FORMAT " was overwritten ("
 411                   SIZE_FORMAT ")", obj, size));
 412   }
 413   return size;
 414 }
 415 
 416 u_char* find_cushion_backwards(u_char* start) {
 417   u_char* p = start;
 418   while (p[ 0] != badResourceValue || p[-1] != badResourceValue ||
 419          p[-2] != badResourceValue || p[-3] != badResourceValue) p--;
 420   // ok, we have four consecutive marker bytes; find start
 421   u_char* q = p - 4;
 422   while (*q == badResourceValue) q--;
 423   return q + 1;
 424 }
 425 
 426 u_char* find_cushion_forwards(u_char* start) {
 427   u_char* p = start;
 428   while (p[0] != badResourceValue || p[1] != badResourceValue ||
 429          p[2] != badResourceValue || p[3] != badResourceValue) p++;
 430   // ok, we have four consecutive marker bytes; find end of cushion
 431   u_char* q = p + 4;
 432   while (*q == badResourceValue) q++;
 433   return q - MallocCushion;
 434 }
 435 
 436 void print_neighbor_blocks(void* ptr) {
 437   // find block allocated before ptr (not entirely crash-proof)
 438   if (MallocCushion < 4) {
 439     tty->print_cr("### cannot find previous block (MallocCushion < 4)");
 440     return;
 441   }
 442   u_char* start_of_this_block = (u_char*)ptr - space_before;
 443   u_char* end_of_prev_block_data = start_of_this_block - space_after -1;
 444   // look for cushion in front of prev. block
 445   u_char* start_of_prev_block = find_cushion_backwards(end_of_prev_block_data);
 446   ptrdiff_t size = *size_addr_from_base(start_of_prev_block);
 447   u_char* obj = start_of_prev_block + space_before;
 448   if (size <= 0 ) {
 449     // start is bad; mayhave been confused by OS data inbetween objects
 450     // search one more backwards
 451     start_of_prev_block = find_cushion_backwards(start_of_prev_block);
 452     size = *size_addr_from_base(start_of_prev_block);
 453     obj = start_of_prev_block + space_before;
 454   }
 455 
 456   if (start_of_prev_block + space_before + size + space_after == start_of_this_block) {
 457     tty->print_cr("### previous object: %p (%ld bytes)", obj, size);
 458   } else {
 459     tty->print_cr("### previous object (not sure if correct): %p (%ld bytes)", obj, size);
 460   }
 461 
 462   // now find successor block
 463   u_char* start_of_next_block = (u_char*)ptr + *size_addr_from_obj(ptr) + space_after;
 464   start_of_next_block = find_cushion_forwards(start_of_next_block);
 465   u_char* next_obj = start_of_next_block + space_before;
 466   ptrdiff_t next_size = *size_addr_from_base(start_of_next_block);
 467   if (start_of_next_block[0] == badResourceValue &&
 468       start_of_next_block[1] == badResourceValue &&
 469       start_of_next_block[2] == badResourceValue &&
 470       start_of_next_block[3] == badResourceValue) {
 471     tty->print_cr("### next object: %p (%ld bytes)", next_obj, next_size);
 472   } else {
 473     tty->print_cr("### next object (not sure if correct): %p (%ld bytes)", next_obj, next_size);
 474   }
 475 }
 476 
 477 
 478 void report_heap_error(void* memblock, void* bad, const char* where) {
 479   tty->print_cr("## nof_mallocs = %d, nof_frees = %d", os::num_mallocs, os::num_frees);
 480   tty->print_cr("## memory stomp: byte at %p %s object %p", bad, where, memblock);
 481   print_neighbor_blocks(memblock);
 482   fatal("memory stomping error");
 483 }
 484 
 485 void verify_block(void* memblock) {
 486   size_t size = get_size(memblock);
 487   if (MallocCushion) {
 488     u_char* ptr = (u_char*)memblock - space_before;
 489     for (int i = 0; i < MallocCushion; i++) {
 490       if (ptr[i] != badResourceValue) {
 491         report_heap_error(memblock, ptr+i, "in front of");
 492       }
 493     }
 494     u_char* end = (u_char*)memblock + size + space_after;
 495     for (int j = -MallocCushion; j < 0; j++) {
 496       if (end[j] != badResourceValue) {
 497         report_heap_error(memblock, end+j, "after");
 498       }
 499     }
 500   }
 501 }
 502 #endif
 503 
 504 void* os::malloc(size_t size) {
 505   NOT_PRODUCT(num_mallocs++);
 506   NOT_PRODUCT(alloc_bytes += size);
 507 
 508   if (size == 0) {
 509     // return a valid pointer if size is zero
 510     // if NULL is returned the calling functions assume out of memory.
 511     size = 1;
 512   }
 513 
 514   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());
 515   u_char* ptr = (u_char*)::malloc(size + space_before + space_after);
 516 #ifdef ASSERT
 517   if (ptr == NULL) return NULL;
 518   if (MallocCushion) {
 519     for (u_char* p = ptr; p < ptr + MallocCushion; p++) *p = (u_char)badResourceValue;
 520     u_char* end = ptr + space_before + size;
 521     for (u_char* pq = ptr+MallocCushion; pq < end; pq++) *pq = (u_char)uninitBlockPad;
 522     for (u_char* q = end; q < end + MallocCushion; q++) *q = (u_char)badResourceValue;
 523   }
 524   // put size just before data
 525   *size_addr_from_base(ptr) = size;
 526 #endif
 527   u_char* memblock = ptr + space_before;
 528   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
 529     tty->print_cr("os::malloc caught, %lu bytes --> %p", size, memblock);
 530     breakpoint();
 531   }
 532   debug_only(if (paranoid) verify_block(memblock));
 533   if (PrintMalloc && tty != NULL) tty->print_cr("os::malloc %lu bytes --> %p", size, memblock);
 534   return memblock;
 535 }
 536 
 537 
 538 void* os::realloc(void *memblock, size_t size) {
 539   NOT_PRODUCT(num_mallocs++);
 540   NOT_PRODUCT(alloc_bytes += size);
 541 #ifndef ASSERT
 542   return ::realloc(memblock, size);
 543 #else
 544   if (memblock == NULL) {
 545     return os::malloc(size);
 546   }
 547   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
 548     tty->print_cr("os::realloc caught %p", memblock);
 549     breakpoint();
 550   }
 551   verify_block(memblock);
 552   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());
 553   if (size == 0) return NULL;
 554   // always move the block
 555   void* ptr = malloc(size);
 556   if (PrintMalloc) tty->print_cr("os::remalloc %lu bytes, %p --> %p", size, memblock, ptr);
 557   // Copy to new memory if malloc didn't fail
 558   if ( ptr != NULL ) {
 559     memcpy(ptr, memblock, MIN2(size, get_size(memblock)));
 560     if (paranoid) verify_block(ptr);
 561     if ((intptr_t)ptr == (intptr_t)MallocCatchPtr) {
 562       tty->print_cr("os::realloc caught, %lu bytes --> %p", size, ptr);
 563       breakpoint();
 564     }
 565     free(memblock);
 566   }
 567   return ptr;
 568 #endif
 569 }
 570 
 571 
 572 void  os::free(void *memblock) {
 573   NOT_PRODUCT(num_frees++);
 574 #ifdef ASSERT
 575   if (memblock == NULL) return;
 576   if ((intptr_t)memblock == (intptr_t)MallocCatchPtr) {
 577     if (tty != NULL) tty->print_cr("os::free caught %p", memblock);
 578     breakpoint();
 579   }
 580   verify_block(memblock);
 581   if (PrintMalloc && tty != NULL)
 582     // tty->print_cr("os::free %p", memblock);
 583     fprintf(stderr, "os::free %p\n", memblock);
 584   NOT_PRODUCT(if (MallocVerifyInterval > 0) check_heap());
 585   // Added by detlefs.
 586   if (MallocCushion) {
 587     u_char* ptr = (u_char*)memblock - space_before;
 588     for (u_char* p = ptr; p < ptr + MallocCushion; p++) {
 589       guarantee(*p == badResourceValue,
 590                 "Thing freed should be malloc result.");
 591       *p = (u_char)freeBlockPad;
 592     }
 593     size_t size = get_size(memblock);
 594     u_char* end = ptr + space_before + size;
 595     for (u_char* q = end; q < end + MallocCushion; q++) {
 596       guarantee(*q == badResourceValue,
 597                 "Thing freed should be malloc result.");
 598       *q = (u_char)freeBlockPad;
 599     }
 600   }
 601 #endif
 602   ::free((char*)memblock - space_before);
 603 }
 604 
 605 void os::init_random(long initval) {
 606   _rand_seed = initval;
 607 }
 608 
 609 
 610 long os::random() {
 611   /* standard, well-known linear congruential random generator with
 612    * next_rand = (16807*seed) mod (2**31-1)
 613    * see
 614    * (1) "Random Number Generators: Good Ones Are Hard to Find",
 615    *      S.K. Park and K.W. Miller, Communications of the ACM 31:10 (Oct 1988),
 616    * (2) "Two Fast Implementations of the 'Minimal Standard' Random
 617    *     Number Generator", David G. Carta, Comm. ACM 33, 1 (Jan 1990), pp. 87-88.
 618   */
 619   const long a = 16807;
 620   const unsigned long m = 2147483647;
 621   const long q = m / a;        assert(q == 127773, "weird math");
 622   const long r = m % a;        assert(r == 2836, "weird math");
 623 
 624   // compute az=2^31p+q
 625   unsigned long lo = a * (long)(_rand_seed & 0xFFFF);
 626   unsigned long hi = a * (long)((unsigned long)_rand_seed >> 16);
 627   lo += (hi & 0x7FFF) << 16;
 628 
 629   // if q overflowed, ignore the overflow and increment q
 630   if (lo > m) {
 631     lo &= m;
 632     ++lo;
 633   }
 634   lo += hi >> 15;
 635 
 636   // if (p+q) overflowed, ignore the overflow and increment (p+q)
 637   if (lo > m) {
 638     lo &= m;
 639     ++lo;
 640   }
 641   return (_rand_seed = lo);
 642 }
 643 
 644 // The INITIALIZED state is distinguished from the SUSPENDED state because the
 645 // conditions in which a thread is first started are different from those in which
 646 // a suspension is resumed.  These differences make it hard for us to apply the
 647 // tougher checks when starting threads that we want to do when resuming them.
 648 // However, when start_thread is called as a result of Thread.start, on a Java
 649 // thread, the operation is synchronized on the Java Thread object.  So there
 650 // cannot be a race to start the thread and hence for the thread to exit while
 651 // we are working on it.  Non-Java threads that start Java threads either have
 652 // to do so in a context in which races are impossible, or should do appropriate
 653 // locking.
 654 
 655 void os::start_thread(Thread* thread) {
 656   // guard suspend/resume
 657   MutexLockerEx ml(thread->SR_lock(), Mutex::_no_safepoint_check_flag);
 658   OSThread* osthread = thread->osthread();
 659   osthread->set_state(RUNNABLE);
 660   pd_start_thread(thread);
 661 }
 662 
 663 //---------------------------------------------------------------------------
 664 // Helper functions for fatal error handler
 665 
 666 void os::print_hex_dump(outputStream* st, address start, address end, int unitsize) {
 667   assert(unitsize == 1 || unitsize == 2 || unitsize == 4 || unitsize == 8, "just checking");
 668 
 669   int cols = 0;
 670   int cols_per_line = 0;
 671   switch (unitsize) {
 672     case 1: cols_per_line = 16; break;
 673     case 2: cols_per_line = 8;  break;
 674     case 4: cols_per_line = 4;  break;
 675     case 8: cols_per_line = 2;  break;
 676     default: return;
 677   }
 678 
 679   address p = start;
 680   st->print(PTR_FORMAT ":   ", start);
 681   while (p < end) {
 682     switch (unitsize) {
 683       case 1: st->print("%02x", *(u1*)p); break;
 684       case 2: st->print("%04x", *(u2*)p); break;
 685       case 4: st->print("%08x", *(u4*)p); break;
 686       case 8: st->print("%016" FORMAT64_MODIFIER "x", *(u8*)p); break;
 687     }
 688     p += unitsize;
 689     cols++;
 690     if (cols >= cols_per_line && p < end) {
 691        cols = 0;
 692        st->cr();
 693        st->print(PTR_FORMAT ":   ", p);
 694     } else {
 695        st->print(" ");
 696     }
 697   }
 698   st->cr();
 699 }
 700 
 701 void os::print_environment_variables(outputStream* st, const char** env_list,
 702                                      char* buffer, int len) {
 703   if (env_list) {
 704     st->print_cr("Environment Variables:");
 705 
 706     for (int i = 0; env_list[i] != NULL; i++) {
 707       if (getenv(env_list[i], buffer, len)) {
 708         st->print(env_list[i]);
 709         st->print("=");
 710         st->print_cr(buffer);
 711       }
 712     }
 713   }
 714 }
 715 
 716 void os::print_cpu_info(outputStream* st) {
 717   // cpu
 718   st->print("CPU:");
 719   st->print("total %d", os::processor_count());
 720   // It's not safe to query number of active processors after crash
 721   // st->print("(active %d)", os::active_processor_count());
 722   st->print(" %s", VM_Version::cpu_features());
 723   st->cr();
 724 }
 725 
 726 void os::print_date_and_time(outputStream *st) {
 727   time_t tloc;
 728   (void)time(&tloc);
 729   st->print("time: %s", ctime(&tloc));  // ctime adds newline.
 730 
 731   double t = os::elapsedTime();
 732   // NOTE: It tends to crash after a SEGV if we want to printf("%f",...) in
 733   //       Linux. Must be a bug in glibc ? Workaround is to round "t" to int
 734   //       before printf. We lost some precision, but who cares?
 735   st->print_cr("elapsed time: %d seconds", (int)t);
 736 }
 737 
 738 // moved from debug.cpp (used to be find()) but still called from there
 739 // The verbose parameter is only set by the debug code in one case
 740 void os::print_location(outputStream* st, intptr_t x, bool verbose) {
 741   address addr = (address)x;
 742   CodeBlob* b = CodeCache::find_blob_unsafe(addr);
 743   if (b != NULL) {
 744     if (b->is_buffer_blob()) {
 745       // the interpreter is generated into a buffer blob
 746       InterpreterCodelet* i = Interpreter::codelet_containing(addr);
 747       if (i != NULL) {
 748         st->print_cr(INTPTR_FORMAT " is an Interpreter codelet", addr);
 749         i->print_on(st);
 750         return;
 751       }
 752       if (Interpreter::contains(addr)) {
 753         st->print_cr(INTPTR_FORMAT " is pointing into interpreter code"
 754                      " (not bytecode specific)", addr);
 755         return;
 756       }
 757       //
 758       if (AdapterHandlerLibrary::contains(b)) {
 759         st->print_cr(INTPTR_FORMAT " is an AdapterHandler", addr);
 760         AdapterHandlerLibrary::print_handler_on(st, b);
 761       }
 762       // the stubroutines are generated into a buffer blob
 763       StubCodeDesc* d = StubCodeDesc::desc_for(addr);
 764       if (d != NULL) {
 765         d->print_on(st);
 766         if (verbose) st->cr();
 767         return;
 768       }
 769       if (StubRoutines::contains(addr)) {
 770         st->print_cr(INTPTR_FORMAT " is pointing to an (unnamed) "
 771                      "stub routine", addr);
 772         return;
 773       }
 774       // the InlineCacheBuffer is using stubs generated into a buffer blob
 775       if (InlineCacheBuffer::contains(addr)) {
 776         st->print_cr(INTPTR_FORMAT " is pointing into InlineCacheBuffer", addr);
 777         return;
 778       }
 779       VtableStub* v = VtableStubs::stub_containing(addr);
 780       if (v != NULL) {
 781         v->print_on(st);
 782         return;
 783       }
 784     }
 785     if (verbose && b->is_nmethod()) {
 786       ResourceMark rm;
 787       st->print("%#p: Compiled ", addr);
 788       ((nmethod*)b)->method()->print_value_on(st);
 789       st->print("  = (CodeBlob*)" INTPTR_FORMAT, b);
 790       st->cr();
 791       return;
 792     }
 793     if ( b->is_nmethod()) {
 794       if (b->is_zombie()) {
 795         st->print_cr(INTPTR_FORMAT " is zombie nmethod", b);
 796       } else if (b->is_not_entrant()) {
 797         st->print_cr(INTPTR_FORMAT " is non-entrant nmethod", b);
 798       }
 799     }
 800     b->print_on(st);
 801     return;
 802   }
 803 
 804   if (Universe::heap()->is_in(addr)) {
 805     HeapWord* p = Universe::heap()->block_start(addr);
 806     bool print = false;
 807     // If we couldn't find it it just may mean that heap wasn't parseable
 808     // See if we were just given an oop directly
 809     if (p != NULL && Universe::heap()->block_is_obj(p)) {
 810       print = true;
 811     } else if (p == NULL && ((oopDesc*)addr)->is_oop()) {
 812       p = (HeapWord*) addr;
 813       print = true;
 814     }
 815     if (print) {
 816       st->print_cr(INTPTR_FORMAT " is an oop", addr);
 817       oop(p)->print_on(st);
 818       if (p != (HeapWord*)x && oop(p)->is_constMethod() &&
 819           constMethodOop(p)->contains(addr)) {
 820         Thread *thread = Thread::current();
 821         HandleMark hm(thread);
 822         methodHandle mh (thread, constMethodOop(p)->method());
 823         if (!mh->is_native()) {
 824           st->print_cr("bci_from(%p) = %d; print_codes():",
 825                         addr, mh->bci_from(address(x)));
 826           mh->print_codes_on(st);
 827         }
 828       }
 829       return;
 830     }
 831   } else {
 832     if (Universe::heap()->is_in_reserved(addr)) {
 833       st->print_cr(INTPTR_FORMAT " is an unallocated location "
 834                    "in the heap", addr);
 835       return;
 836     }
 837   }
 838   if (JNIHandles::is_global_handle((jobject) addr)) {
 839     st->print_cr(INTPTR_FORMAT " is a global jni handle", addr);
 840     return;
 841   }
 842   if (JNIHandles::is_weak_global_handle((jobject) addr)) {
 843     st->print_cr(INTPTR_FORMAT " is a weak global jni handle", addr);
 844     return;
 845   }
 846 #ifndef PRODUCT
 847   // we don't keep the block list in product mode
 848   if (JNIHandleBlock::any_contains((jobject) addr)) {
 849     st->print_cr(INTPTR_FORMAT " is a local jni handle", addr);
 850     return;
 851   }
 852 #endif
 853 
 854   for(JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
 855     // Check for privilege stack
 856     if (thread->privileged_stack_top() != NULL &&
 857         thread->privileged_stack_top()->contains(addr)) {
 858       st->print_cr(INTPTR_FORMAT " is pointing into the privilege stack "
 859                    "for thread: " INTPTR_FORMAT, addr, thread);
 860       if (verbose) thread->print_on(st);
 861       return;
 862     }
 863     // If the addr is a java thread print information about that.
 864     if (addr == (address)thread) {
 865       if (verbose) {
 866         thread->print_on(st);
 867       } else {
 868         st->print_cr(INTPTR_FORMAT " is a thread", addr);
 869       }
 870       return;
 871     }
 872     // If the addr is in the stack region for this thread then report that
 873     // and print thread info
 874     if (thread->stack_base() >= addr &&
 875         addr > (thread->stack_base() - thread->stack_size())) {
 876       st->print_cr(INTPTR_FORMAT " is pointing into the stack for thread: "
 877                    INTPTR_FORMAT, addr, thread);
 878       if (verbose) thread->print_on(st);
 879       return;
 880     }
 881 
 882   }
 883   // Try an OS specific find
 884   if (os::find(addr, st)) {
 885     return;
 886   }
 887 
 888   st->print_cr(INTPTR_FORMAT " is an unknown value", addr);
 889 }
 890 
 891 // Looks like all platforms except IA64 can use the same function to check
 892 // if C stack is walkable beyond current frame. The check for fp() is not
 893 // necessary on Sparc, but it's harmless.
 894 bool os::is_first_C_frame(frame* fr) {
 895 #ifdef IA64
 896   // In order to walk native frames on Itanium, we need to access the unwind
 897   // table, which is inside ELF. We don't want to parse ELF after fatal error,
 898   // so return true for IA64. If we need to support C stack walking on IA64,
 899   // this function needs to be moved to CPU specific files, as fp() on IA64
 900   // is register stack, which grows towards higher memory address.
 901   return true;
 902 #endif
 903 
 904   // Load up sp, fp, sender sp and sender fp, check for reasonable values.
 905   // Check usp first, because if that's bad the other accessors may fault
 906   // on some architectures.  Ditto ufp second, etc.
 907   uintptr_t fp_align_mask = (uintptr_t)(sizeof(address)-1);
 908   // sp on amd can be 32 bit aligned.
 909   uintptr_t sp_align_mask = (uintptr_t)(sizeof(int)-1);
 910 
 911   uintptr_t usp    = (uintptr_t)fr->sp();
 912   if ((usp & sp_align_mask) != 0) return true;
 913 
 914   uintptr_t ufp    = (uintptr_t)fr->fp();
 915   if ((ufp & fp_align_mask) != 0) return true;
 916 
 917   uintptr_t old_sp = (uintptr_t)fr->sender_sp();
 918   if ((old_sp & sp_align_mask) != 0) return true;
 919   if (old_sp == 0 || old_sp == (uintptr_t)-1) return true;
 920 
 921   uintptr_t old_fp = (uintptr_t)fr->link();
 922   if ((old_fp & fp_align_mask) != 0) return true;
 923   if (old_fp == 0 || old_fp == (uintptr_t)-1 || old_fp == ufp) return true;
 924 
 925   // stack grows downwards; if old_fp is below current fp or if the stack
 926   // frame is too large, either the stack is corrupted or fp is not saved
 927   // on stack (i.e. on x86, ebp may be used as general register). The stack
 928   // is not walkable beyond current frame.
 929   if (old_fp < ufp) return true;
 930   if (old_fp - ufp > 64 * K) return true;
 931 
 932   return false;
 933 }
 934 
 935 #ifdef ASSERT
 936 extern "C" void test_random() {
 937   const double m = 2147483647;
 938   double mean = 0.0, variance = 0.0, t;
 939   long reps = 10000;
 940   unsigned long seed = 1;
 941 
 942   tty->print_cr("seed %ld for %ld repeats...", seed, reps);
 943   os::init_random(seed);
 944   long num;
 945   for (int k = 0; k < reps; k++) {
 946     num = os::random();
 947     double u = (double)num / m;
 948     assert(u >= 0.0 && u <= 1.0, "bad random number!");
 949 
 950     // calculate mean and variance of the random sequence
 951     mean += u;
 952     variance += (u*u);
 953   }
 954   mean /= reps;
 955   variance /= (reps - 1);
 956 
 957   assert(num == 1043618065, "bad seed");
 958   tty->print_cr("mean of the 1st 10000 numbers: %f", mean);
 959   tty->print_cr("variance of the 1st 10000 numbers: %f", variance);
 960   const double eps = 0.0001;
 961   t = fabsd(mean - 0.5018);
 962   assert(t < eps, "bad mean");
 963   t = (variance - 0.3355) < 0.0 ? -(variance - 0.3355) : variance - 0.3355;
 964   assert(t < eps, "bad variance");
 965 }
 966 #endif
 967 
 968 
 969 // Set up the boot classpath.
 970 
 971 char* os::format_boot_path(const char* format_string,
 972                            const char* home,
 973                            int home_len,
 974                            char fileSep,
 975                            char pathSep) {
 976     assert((fileSep == '/' && pathSep == ':') ||
 977            (fileSep == '\\' && pathSep == ';'), "unexpected seperator chars");
 978 
 979     // Scan the format string to determine the length of the actual
 980     // boot classpath, and handle platform dependencies as well.
 981     int formatted_path_len = 0;
 982     const char* p;
 983     for (p = format_string; *p != 0; ++p) {
 984         if (*p == '%') formatted_path_len += home_len - 1;
 985         ++formatted_path_len;
 986     }
 987 
 988     char* formatted_path = NEW_C_HEAP_ARRAY(char, formatted_path_len + 1);
 989     if (formatted_path == NULL) {
 990         return NULL;
 991     }
 992 
 993     // Create boot classpath from format, substituting separator chars and
 994     // java home directory.
 995     char* q = formatted_path;
 996     for (p = format_string; *p != 0; ++p) {
 997         switch (*p) {
 998         case '%':
 999             strcpy(q, home);
1000             q += home_len;
1001             break;
1002         case '/':
1003             *q++ = fileSep;
1004             break;
1005         case ':':
1006             *q++ = pathSep;
1007             break;
1008         default:
1009             *q++ = *p;
1010         }
1011     }
1012     *q = '\0';
1013 
1014     assert((q - formatted_path) == formatted_path_len, "formatted_path size botched");
1015     return formatted_path;
1016 }
1017 
1018 
1019 bool os::set_boot_path(char fileSep, char pathSep) {
1020     const char* home = Arguments::get_java_home();
1021     int home_len = (int)strlen(home);
1022 
1023     static const char* meta_index_dir_format = "%/lib/";
1024     static const char* meta_index_format = "%/lib/meta-index";
1025     char* meta_index = format_boot_path(meta_index_format, home, home_len, fileSep, pathSep);
1026     if (meta_index == NULL) return false;
1027     char* meta_index_dir = format_boot_path(meta_index_dir_format, home, home_len, fileSep, pathSep);
1028     if (meta_index_dir == NULL) return false;
1029     Arguments::set_meta_index_path(meta_index, meta_index_dir);
1030 
1031     // Any modification to the JAR-file list, for the boot classpath must be
1032     // aligned with install/install/make/common/Pack.gmk. Note: boot class
1033     // path class JARs, are stripped for StackMapTable to reduce download size.
1034     static const char classpath_format[] =
1035         "%/lib/resources.jar:"
1036         "%/lib/rt.jar:"
1037         "%/lib/sunrsasign.jar:"
1038         "%/lib/jsse.jar:"
1039         "%/lib/jce.jar:"
1040         "%/lib/charsets.jar:"
1041 
1042         // ## TEMPORARY hack to keep the legacy launcher working when
1043         // ## only the boot module is installed (cf. j.l.ClassLoader)
1044         "%/lib/modules/jdk.boot.jar:"
1045 
1046         "%/classes";
1047     char* sysclasspath = format_boot_path(classpath_format, home, home_len, fileSep, pathSep);
1048     if (sysclasspath == NULL) return false;
1049     Arguments::set_sysclasspath(sysclasspath);
1050 
1051     return true;
1052 }
1053 
1054 /*
1055  * Splits a path, based on its separator, the number of
1056  * elements is returned back in n.
1057  * It is the callers responsibility to:
1058  *   a> check the value of n, and n may be 0.
1059  *   b> ignore any empty path elements
1060  *   c> free up the data.
1061  */
1062 char** os::split_path(const char* path, int* n) {
1063   *n = 0;
1064   if (path == NULL || strlen(path) == 0) {
1065     return NULL;
1066   }
1067   const char psepchar = *os::path_separator();
1068   char* inpath = (char*)NEW_C_HEAP_ARRAY(char, strlen(path) + 1);
1069   if (inpath == NULL) {
1070     return NULL;
1071   }
1072   strncpy(inpath, path, strlen(path));
1073   int count = 1;
1074   char* p = strchr(inpath, psepchar);
1075   // Get a count of elements to allocate memory
1076   while (p != NULL) {
1077     count++;
1078     p++;
1079     p = strchr(p, psepchar);
1080   }
1081   char** opath = (char**) NEW_C_HEAP_ARRAY(char*, count);
1082   if (opath == NULL) {
1083     return NULL;
1084   }
1085 
1086   // do the actual splitting
1087   p = inpath;
1088   for (int i = 0 ; i < count ; i++) {
1089     size_t len = strcspn(p, os::path_separator());
1090     if (len > JVM_MAXPATHLEN) {
1091       return NULL;
1092     }
1093     // allocate the string and add terminator storage
1094     char* s  = (char*)NEW_C_HEAP_ARRAY(char, len + 1);
1095     if (s == NULL) {
1096       return NULL;
1097     }
1098     strncpy(s, p, len);
1099     s[len] = '\0';
1100     opath[i] = s;
1101     p += len + 1;
1102   }
1103   FREE_C_HEAP_ARRAY(char, inpath);
1104   *n = count;
1105   return opath;
1106 }
1107 
1108 void os::set_memory_serialize_page(address page) {
1109   int count = log2_intptr(sizeof(class JavaThread)) - log2_intptr(64);
1110   _mem_serialize_page = (volatile int32_t *)page;
1111   // We initialize the serialization page shift count here
1112   // We assume a cache line size of 64 bytes
1113   assert(SerializePageShiftCount == count,
1114          "thread size changed, fix SerializePageShiftCount constant");
1115   set_serialize_page_mask((uintptr_t)(vm_page_size() - sizeof(int32_t)));
1116 }
1117 
1118 static volatile intptr_t SerializePageLock = 0;
1119 
1120 // This method is called from signal handler when SIGSEGV occurs while the current
1121 // thread tries to store to the "read-only" memory serialize page during state
1122 // transition.
1123 void os::block_on_serialize_page_trap() {
1124   if (TraceSafepoint) {
1125     tty->print_cr("Block until the serialize page permission restored");
1126   }
1127   // When VMThread is holding the SerializePageLock during modifying the
1128   // access permission of the memory serialize page, the following call
1129   // will block until the permission of that page is restored to rw.
1130   // Generally, it is unsafe to manipulate locks in signal handlers, but in
1131   // this case, it's OK as the signal is synchronous and we know precisely when
1132   // it can occur.
1133   Thread::muxAcquire(&SerializePageLock, "set_memory_serialize_page");
1134   Thread::muxRelease(&SerializePageLock);
1135 }
1136 
1137 // Serialize all thread state variables
1138 void os::serialize_thread_states() {
1139   // On some platforms such as Solaris & Linux, the time duration of the page
1140   // permission restoration is observed to be much longer than expected  due to
1141   // scheduler starvation problem etc. To avoid the long synchronization
1142   // time and expensive page trap spinning, 'SerializePageLock' is used to block
1143   // the mutator thread if such case is encountered. See bug 6546278 for details.
1144   Thread::muxAcquire(&SerializePageLock, "serialize_thread_states");
1145   os::protect_memory((char *)os::get_memory_serialize_page(),
1146                      os::vm_page_size(), MEM_PROT_READ);
1147   os::protect_memory((char *)os::get_memory_serialize_page(),
1148                      os::vm_page_size(), MEM_PROT_RW);
1149   Thread::muxRelease(&SerializePageLock);
1150 }
1151 
1152 // Returns true if the current stack pointer is above the stack shadow
1153 // pages, false otherwise.
1154 
1155 bool os::stack_shadow_pages_available(Thread *thread, methodHandle method) {
1156   assert(StackRedPages > 0 && StackYellowPages > 0,"Sanity check");
1157   address sp = current_stack_pointer();
1158   // Check if we have StackShadowPages above the yellow zone.  This parameter
1159   // is dependent on the depth of the maximum VM call stack possible from
1160   // the handler for stack overflow.  'instanceof' in the stack overflow
1161   // handler or a println uses at least 8k stack of VM and native code
1162   // respectively.
1163   const int framesize_in_bytes =
1164     Interpreter::size_top_interpreter_activation(method()) * wordSize;
1165   int reserved_area = ((StackShadowPages + StackRedPages + StackYellowPages)
1166                       * vm_page_size()) + framesize_in_bytes;
1167   // The very lower end of the stack
1168   address stack_limit = thread->stack_base() - thread->stack_size();
1169   return (sp > (stack_limit + reserved_area));
1170 }
1171 
1172 size_t os::page_size_for_region(size_t region_min_size, size_t region_max_size,
1173                                 uint min_pages)
1174 {
1175   assert(min_pages > 0, "sanity");
1176   if (UseLargePages) {
1177     const size_t max_page_size = region_max_size / min_pages;
1178 
1179     for (unsigned int i = 0; _page_sizes[i] != 0; ++i) {
1180       const size_t sz = _page_sizes[i];
1181       const size_t mask = sz - 1;
1182       if ((region_min_size & mask) == 0 && (region_max_size & mask) == 0) {
1183         // The largest page size with no fragmentation.
1184         return sz;
1185       }
1186 
1187       if (sz <= max_page_size) {
1188         // The largest page size that satisfies the min_pages requirement.
1189         return sz;
1190       }
1191     }
1192   }
1193 
1194   return vm_page_size();
1195 }
1196 
1197 #ifndef PRODUCT
1198 void os::trace_page_sizes(const char* str, const size_t region_min_size,
1199                           const size_t region_max_size, const size_t page_size,
1200                           const char* base, const size_t size)
1201 {
1202   if (TracePageSizes) {
1203     tty->print_cr("%s:  min=" SIZE_FORMAT " max=" SIZE_FORMAT
1204                   " pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT
1205                   " size=" SIZE_FORMAT,
1206                   str, region_min_size, region_max_size,
1207                   page_size, base, size);
1208   }
1209 }
1210 #endif  // #ifndef PRODUCT
1211 
1212 // This is the working definition of a server class machine:
1213 // >= 2 physical CPU's and >=2GB of memory, with some fuzz
1214 // because the graphics memory (?) sometimes masks physical memory.
1215 // If you want to change the definition of a server class machine
1216 // on some OS or platform, e.g., >=4GB on Windohs platforms,
1217 // then you'll have to parameterize this method based on that state,
1218 // as was done for logical processors here, or replicate and
1219 // specialize this method for each platform.  (Or fix os to have
1220 // some inheritance structure and use subclassing.  Sigh.)
1221 // If you want some platform to always or never behave as a server
1222 // class machine, change the setting of AlwaysActAsServerClassMachine
1223 // and NeverActAsServerClassMachine in globals*.hpp.
1224 bool os::is_server_class_machine() {
1225   // First check for the early returns
1226   if (NeverActAsServerClassMachine) {
1227     return false;
1228   }
1229   if (AlwaysActAsServerClassMachine) {
1230     return true;
1231   }
1232   // Then actually look at the machine
1233   bool         result            = false;
1234   const unsigned int    server_processors = 2;
1235   const julong server_memory     = 2UL * G;
1236   // We seem not to get our full complement of memory.
1237   //     We allow some part (1/8?) of the memory to be "missing",
1238   //     based on the sizes of DIMMs, and maybe graphics cards.
1239   const julong missing_memory   = 256UL * M;
1240 
1241   /* Is this a server class machine? */
1242   if ((os::active_processor_count() >= (int)server_processors) &&
1243       (os::physical_memory() >= (server_memory - missing_memory))) {
1244     const unsigned int logical_processors =
1245       VM_Version::logical_processors_per_package();
1246     if (logical_processors > 1) {
1247       const unsigned int physical_packages =
1248         os::active_processor_count() / logical_processors;
1249       if (physical_packages > server_processors) {
1250         result = true;
1251       }
1252     } else {
1253       result = true;
1254     }
1255   }
1256   return result;
1257 }