# HG changeset patch
# User tschatzl
# Date 1492496746 -3600
# Node ID 8ba07ad46983953ef1b13187462a48dac5b24c8d
# Parent  bbd1934c49f740c3a7ceaded63350664b9aec003
8147910: Cache initial active_processor_count
Summary: Introduce and initialize active_processor_count variable in VM.
Reviewed-by: dholmes, jprovino

diff -r bbd1934c49f7 -r 8ba07ad46983 src/share/vm/runtime/os.cpp
--- a/src/share/vm/runtime/os.cpp	Tue Apr 18 07:03:25 2017 +0100
+++ b/src/share/vm/runtime/os.cpp	Tue Apr 18 07:25:46 2017 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2016, 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
@@ -78,6 +78,7 @@
 uintptr_t         os::_serialize_page_mask = 0;
 long              os::_rand_seed          = 1;
 int               os::_processor_count    = 0;
+int               os::_initial_active_processor_count = 0;
 size_t            os::_page_sizes[os::page_sizes_max];
 
 #ifndef PRODUCT
@@ -314,6 +315,7 @@
 }
 
 void os::init_before_ergo() {
+  initialize_initial_active_processor_count();
   // We need to initialize large page support here because ergonomics takes some
   // decisions depending on large page support and the calculated large page size.
   large_page_init();
@@ -820,7 +822,11 @@
   st->print("CPU:");
   st->print("total %d", os::processor_count());
   // It's not safe to query number of active processors after crash
-  // st->print("(active %d)", os::active_processor_count());
+  // st->print("(active %d)", os::active_processor_count()); but we can
+  // print the initial number of active processors.
+  // We access the raw value here because the assert in the accessor will
+  // fail if the crash occurs before initialization of this value.
+  st->print(" (initial active %d)", _initial_active_processor_count);
   st->print(" %s", VM_Version::cpu_features());
   st->cr();
   pd_print_cpu_info(st);
@@ -1410,6 +1416,11 @@
   return (int) i;
 }
 
+void os::initialize_initial_active_processor_count() {
+  assert(_initial_active_processor_count == 0, "Initial active processor count already set.");
+  _initial_active_processor_count = active_processor_count();
+}
+
 void os::SuspendedThreadTask::run() {
   assert(Threads_lock->owned_by_self() || (_thread == VMThread::vm_thread()), "must have threads lock to call this");
   internal_do_task();
diff -r bbd1934c49f7 -r 8ba07ad46983 src/share/vm/runtime/os.hpp
--- a/src/share/vm/runtime/os.hpp	Tue Apr 18 07:03:25 2017 +0100
+++ b/src/share/vm/runtime/os.hpp	Tue Apr 18 07:25:46 2017 +0100
@@ -139,6 +139,7 @@
   static void   pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 
 
+  static void initialize_initial_active_processor_count();
  public:
   static void init(void);                      // Called before command line parsing
   static void init_before_ergo(void);          // Called after command line parsing
@@ -218,6 +219,13 @@
   // Note that on some OSes this can change dynamically.
   static int active_processor_count();
 
+  // At startup the number of active CPUs this process is allowed to run on.
+  // This value does not change dynamically. May be different from active_processor_count().
+  static int initial_active_processor_count() {
+    assert(_initial_active_processor_count > 0, "Initial active processor count not set yet.");
+    return _initial_active_processor_count;
+  }
+
   // Bind processes to processors.
   //     This is a two step procedure:
   //     first you generate a distribution of processes to processors,
@@ -935,8 +943,9 @@
 
 
  protected:
-  static long _rand_seed;                   // seed for random number generator
-  static int _processor_count;              // number of processors
+  static long _rand_seed;                     // seed for random number generator
+  static int _processor_count;                // number of processors
+  static int _initial_active_processor_count; // number of active processors during initialization.
 
   static char* format_boot_path(const char* format_string,
                                 const char* home,