changeset 40011:e93911497588

8147910: Cache initial active_processor_count Summary: Introduce and initialize active_processor_count variable in VM. Reviewed-by: dholmes, jprovino
author tschatzl
date Tue, 26 Jul 2016 11:04:20 +0200
parents e32d5e545789
children f69cfe79fe98
files hotspot/src/share/vm/runtime/os.cpp hotspot/src/share/vm/runtime/os.hpp
diffstat 2 files changed, 24 insertions(+), 3 deletions(-) [+]
line wrap: on
line diff
--- a/hotspot/src/share/vm/runtime/os.cpp	Wed Jul 13 12:23:05 2016 +0200
+++ b/hotspot/src/share/vm/runtime/os.cpp	Tue Jul 26 11:04:20 2016 +0200
@@ -71,6 +71,7 @@
 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
@@ -315,6 +316,7 @@
 }
 
 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();
@@ -829,7 +831,11 @@
   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::features_string());
   st->cr();
   pd_print_cpu_info(st, buf, buflen);
@@ -1597,6 +1603,12 @@
   return result;
 }
 
+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();
+  log_debug(os)("Initial active processor count set to %d" , _initial_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();
--- a/hotspot/src/share/vm/runtime/os.hpp	Wed Jul 13 12:23:05 2016 +0200
+++ b/hotspot/src/share/vm/runtime/os.hpp	Tue Jul 26 11:04:20 2016 +0200
@@ -140,6 +140,7 @@
   static void  get_summary_cpu_info(char* buf, size_t buflen);
   static void  get_summary_os_info(char* buf, size_t buflen);
 
+  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
@@ -227,6 +228,13 @@
   // 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,
@@ -948,8 +956,9 @@
 
 
  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,