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 /*

  * Copyright (c) 2014, 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 "memory/allocation.inline.hpp"

 #include "runtime/atomic.hpp"

 #include "services/mallocSiteTable.hpp"

 /*

  * Early os::malloc() calls come from initializations of static variables, long before entering any

  * VM code. Upon the arrival of the first os::malloc() call, malloc site hashtable has to be

  * initialized, along with the allocation site for the hashtable entries.

  * To ensure that malloc site hashtable can be initialized without triggering any additional os::malloc()

  * call, the hashtable bucket array and hashtable entry allocation site have to be static.

  * It is not a problem for hashtable bucket, since it is an array of pointer type, C runtime just

  * allocates a block memory and zero the memory for it.

  * But for hashtable entry allocation site object, things get tricky. C runtime not only allocates

  * memory for it, but also calls its constructor at some later time. If we initialize the allocation site

  * at the first os::malloc() call, the object will be reinitialized when its constructor is called

  * by C runtime.

  * To workaround above issue, we declare a static size_t array with the size of the CallsiteHashtableEntry,

  * the memory is used to instantiate CallsiteHashtableEntry for the hashtable entry allocation site.

  * Given it is a primitive type array, C runtime will do nothing other than assign the memory block for the variable,

  * which is exactly what we want.

  * The same trick is also applied to create NativeCallStack object for CallsiteHashtableEntry memory allocation.

  *

  * Note: C++ object usually aligns to particular alignment, depends on compiler implementation, we declare

  * the memory as size_t arrays, to ensure the memory is aligned to native machine word alignment.

  */

 // Reserve enough memory for NativeCallStack and MallocSiteHashtableEntry objects

 size_t MallocSiteTable::_hash_entry_allocation_stack[CALC_OBJ_SIZE_IN_TYPE(NativeCallStack, size_t)];

 size_t MallocSiteTable::_hash_entry_allocation_site[CALC_OBJ_SIZE_IN_TYPE(MallocSiteHashtableEntry, size_t)];

 // Malloc site hashtable buckets

 MallocSiteHashtableEntry*  MallocSiteTable::_table[MallocSiteTable::table_size];

 // concurrent access counter

 volatile int MallocSiteTable::_access_count = 0;

 // Tracking hashtable contention

 NOT_PRODUCT(int MallocSiteTable::_peak_count = 0;)

 /*

  * Initialize malloc site table.

  * Hashtable entry is malloc'd, so it can cause infinite recursion.

  * To avoid above problem, we pre-initialize a hash entry for

  * this allocation site.

  * The method is called during C runtime static variable initialization

  * time, it is in single-threaded mode from JVM perspective.

  */

 bool MallocSiteTable::initialize() {

   assert(sizeof(_hash_entry_allocation_stack) >= sizeof(NativeCallStack), "Sanity Check");

   assert(sizeof(_hash_entry_allocation_site) >= sizeof(MallocSiteHashtableEntry),

     "Sanity Check");

   assert((size_t)table_size <= MAX_MALLOCSITE_TABLE_SIZE, "Hashtable overflow");

   // Fake the call stack for hashtable entry allocation

   assert(NMT_TrackingStackDepth > 1, "At least one tracking stack");

   // Create pseudo call stack for hashtable entry allocation

   address pc[3];

   if (NMT_TrackingStackDepth >= 3) {

     pc[2] = (address)MallocSiteTable::allocation_at;

   }

   if (NMT_TrackingStackDepth >= 2) {

     pc[1] = (address)MallocSiteTable::lookup_or_add;

   }

   pc[0] = (address)MallocSiteTable::new_entry;

   // Instantiate NativeCallStack object, have to use placement new operator. (see comments above)

   NativeCallStack* stack = ::new ((void*)_hash_entry_allocation_stack)

     NativeCallStack(pc, MIN2(((int)(sizeof(pc) / sizeof(address))), ((int)NMT_TrackingStackDepth)));

   // Instantiate hash entry for hashtable entry allocation callsite

   MallocSiteHashtableEntry* entry = ::new ((void*)_hash_entry_allocation_site)

     MallocSiteHashtableEntry(*stack);

   // Add the allocation site to hashtable.

   int index = hash_to_index(stack->hash());

   _table[index] = entry;

   return true;

 }

 // Walks entries in the hashtable.

 // It stops walk if the walker returns false.

 bool MallocSiteTable::walk(MallocSiteWalker* walker) {

   MallocSiteHashtableEntry* head;

   for (int index = 0; index < table_size; index ++) {

     head = _table[index];

     while (head != NULL) {

       if (!walker->do_malloc_site(head->peek())) {

         return false;

       }

       head = (MallocSiteHashtableEntry*)head->next();

     }

   }

   return true;

 }

 /*

  *  The hashtable does not have deletion policy on individual entry,

  *  and each linked list node is inserted via compare-and-swap,

  *  so each linked list is stable, the contention only happens

  *  at the end of linked list.

  *  This method should not return NULL under normal circumstance.

  *  If NULL is returned, it indicates:

  *    1. Out of memory, it cannot allocate new hash entry.

  *    2. Overflow hash bucket.

  *  Under any of above circumstances, caller should handle the situation.

  */

 MallocSite* MallocSiteTable::lookup_or_add(const NativeCallStack& key, size_t* bucket_idx,

   size_t* pos_idx) {

   int index = hash_to_index(key.hash());

   assert(index >= 0, "Negative index");

   *bucket_idx = (size_t)index;

   *pos_idx = 0;

   // First entry for this hash bucket

   if (_table[index] == NULL) {

     MallocSiteHashtableEntry* entry = new_entry(key);

     // OOM check

     if (entry == NULL) return NULL;

     // swap in the head

     if (Atomic::cmpxchg_ptr((void*)entry, (volatile void *)&_table[index], NULL) == NULL) {

       return entry->data();

     }

     delete entry;

   }

   MallocSiteHashtableEntry* head = _table[index];

   while (head != NULL && (*pos_idx) <= MAX_BUCKET_LENGTH) {

     MallocSite* site = head->data();

     if (site->equals(key)) {

       // found matched entry

       return head->data();

     }

     if (head->next() == NULL && (*pos_idx) < MAX_BUCKET_LENGTH) {

       MallocSiteHashtableEntry* entry = new_entry(key);

       // OOM check

       if (entry == NULL) return NULL;

       if (head->atomic_insert(entry)) {

         (*pos_idx) ++;

         return entry->data();

       }

       // contended, other thread won

       delete entry;

     }

     head = (MallocSiteHashtableEntry*)head->next();

     (*pos_idx) ++;

   }

   return NULL;

 }

 // Access malloc site

 MallocSite* MallocSiteTable::malloc_site(size_t bucket_idx, size_t pos_idx) {

   assert(bucket_idx < table_size, "Invalid bucket index");

   MallocSiteHashtableEntry* head = _table[bucket_idx];

   for (size_t index = 0; index < pos_idx && head != NULL;

     index ++, head = (MallocSiteHashtableEntry*)head->next());

   assert(head != NULL, "Invalid position index");

   return head->data();

 }

 // Allocates MallocSiteHashtableEntry object. Special call stack

 // (pre-installed allocation site) has to be used to avoid infinite

 // recursion.

 MallocSiteHashtableEntry* MallocSiteTable::new_entry(const NativeCallStack& key) {

   void* p = AllocateHeap(sizeof(MallocSiteHashtableEntry), mtNMT,

     *hash_entry_allocation_stack(), AllocFailStrategy::RETURN_NULL);

   return ::new (p) MallocSiteHashtableEntry(key);

 }

 void MallocSiteTable::reset() {

   for (int index = 0; index < table_size; index ++) {

     MallocSiteHashtableEntry* head = _table[index];

     _table[index] = NULL;

     delete_linked_list(head);

   }

 }

 void MallocSiteTable::delete_linked_list(MallocSiteHashtableEntry* head) {

   MallocSiteHashtableEntry* p;

   while (head != NULL) {

     p = head;

     head = (MallocSiteHashtableEntry*)head->next();

     if (p != (MallocSiteHashtableEntry*)_hash_entry_allocation_site) {

       delete p;

     }

   }

 }

 void MallocSiteTable::shutdown() {

   AccessLock locker(&_access_count);

   locker.exclusiveLock();

   reset();

 }

 bool MallocSiteTable::walk_malloc_site(MallocSiteWalker* walker) {

   assert(walker != NULL, "NuLL walker");

   AccessLock locker(&_access_count);

   if (locker.sharedLock()) {

     NOT_PRODUCT(_peak_count = MAX2(_peak_count, _access_count);)

     return walk(walker);

   }

   return false;

 }

 void MallocSiteTable::AccessLock::exclusiveLock() {

   jint target;

   jint val;

   assert(_lock_state != ExclusiveLock, "Can only call once");

   assert(*_lock >= 0, "Can not content exclusive lock");

   // make counter negative to block out shared locks

   do {

     val = *_lock;

     target = _MAGIC_ + *_lock;

   } while (Atomic::cmpxchg(target, _lock, val) != val);

   // wait for all readers to exit

   while (*_lock != _MAGIC_) {

 #ifdef _WINDOWS

     os::naked_short_sleep(1);

 #else

     os::NakedYield();

 #endif

   }

   _lock_state = ExclusiveLock;

 }