Abstract:
A system and method for fast referencing a reference counted item is provided. The system provides for establishing a reference counted item, establishing a fast referencing item, setting a pointer to the reference counted item and storing a local copy of the reference counted item in the pointer to the reference counted item, the pointer being associated with the fast referencing item. The system and method thus allow items to obtain references to the reference counted item from the fast referencing item without employing a locking algorithm wherein the reference counted item is locked, accessed, and unlocked.

Description:
REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/244,314, which was filed Oct. 30, 2000, entitled SYSTEM AND METHOD FOR FAST REFERENCING A REFERENCE COUNTED ITEM. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to computer programming. More particularly the invention relates to fast referencing of a reference counted item. 
     BACKGROUND 
     Reference counting is employed in memory management systems. A reference counted item keeps a count of how many references there are thereto. Items to which there are no references may be reclaimed as available memory. Reference counts are typically begun at a count of one, incremented by one for each reference added, and decremented by one for each reference removed. In such a system, when a reference count falls to zero, the item is no longer required and may be recycled, thus freeing associated memory. Maintaining an accurate reference count is important to memory management. For example, if a reference count indicated that there were no references to an item, and there was an application referring to the reference counted item, and the reference counted item was deleted, then the application could experience an “unresolved pointer” problem, or the application could be reading memory that no longer represented the item associated with the application. By way of further illustration, if a reference count indicated that there were references to an item, but there was no entity referring to that item, then the item would not be reclaimed, and the system with which the reference counted item was associated could suffer from a “memory leak” problem. Thus, it is important to ensure that reference counts are accurately maintained. Therefore, reference counts are frequently protected by locks, which facilitate only one entity accessing a reference count at one time, which mitigates unresolved pointer and memory leak problems. But the locking mechanism creates contention problems, when, for example, two or more entities seek to acquire the lock at the same point in time. Entities other than the entity that acquired the lock must wait, which negatively impacts system performance. 
     Operating systems, multi-threaded applications, and servers, for example, often maintain data structures with which changeable sub-data is associated. For example, a user of a computer system may have a profile, which includes a set of access rights (e.g. can read files, cannot write files). To access the sub-data, (e.g. the access rights) a conventional reference counting method acquires a lock protecting the pointer to the sub-data, fetches the pointer to the sub-data, increments the reference count associated with the sub-data and then releases the lock. Thus, locking and unlocking operations are employed for each access of the sub-data, which slows down processing of such operating systems, multi-threaded applications and servers, for example, due to the contention problem described above. As the number of concurrent processors accessing the sub-data increases, the performance of the conventional lock, fetch, increment, release lock method declines rapidly as more entities contend for the lock. Such a method is particularly wasteful of system resources (e.g. cpu cycles) when the sub-data is frequently read but rarely changed. 
     Thus, a system and method for fast referencing a reference counted item where the performance of the method does not decline so rapidly is required. 
     SUMMARY 
     The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
     The present invention provides a system and method for fast referencing a reference counted item to facilitate performance of multi-threaded applications and/or systems employing concurrent processors. In the present invention, a fast referencing item establishes a reference count in the reference counted item to a value greater than one, establishes a pointer to the reference counted item and stores a local value associated with the reference count, known as a fast reference count (FRC). The initial FRC value is greater than the number of referencing items referencing the reference counted item. 
     By establishing the number of references in the reference counted item at more than one, the referencing item can be viewed as having acquired more than one reference. The “extra” references are then available to subsequent items seeking a reference to the reference counted item, and under certain conditions, such subsequent acquiring items will not be required to acquire a lock, change the reference count and release the lock. Rather, the subsequent acquiring items may examine the number of references available in the fast referencing item and acquire (e.g. “steal/borrow”) one or more of the “extra” references. When acquiring a reference using this method, an atomic operation (e.g. InterlockedCompareExchange( )) is employed to change the FRC in the fast referencing item to facilitate maintaining an accurate count of the references to the reference counted item. A fast referencing item that acquires more than one reference, can itself be examined for available references and can have one or more of its available references acquired. 
     The FRC may be stored in a variable, or in one or more bits in the pointer. Such bits may be available if, for example, the reference counted item is located in a memory area where items are aligned on eight byte boundaries (freeing, for example, the low order three bits of the pointer), or if other bits in the pointer are available. The bits employed to store the FRC may be contiguous in the pointer, or they may be distributed throughout the pointer. 
     The system and method thus facilitates obtaining references to a reference counted item without employing a locking algorithm wherein a lock is acquired, a reference is acquired and the lock is released. Thus, performance degradation due to contention problems that arise when multiple entities are seeking to acquire the lock to the reference counted item is mitigated. 
    
    
     To the accomplishment of the foregoing and related ends, certain illustrative aspects of the invention are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention may become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is schematic block diagram illustrating a reference counted item being accessed in accordance with an aspect of the present invention. 
     FIG. 1B is a schematic block diagram illustrating a fast referencing count associated with a fast referencing item in accordance with an aspect of the present invention. 
     FIG. 2 illustrates a local value associated with the reference count in a reference counted item being stored in a pointer to the reference counted item in accordance with an aspect of the present invention. 
     FIG. 3 illustrates a conventional pointer and a pointer adapted to store a local value associated with a reference count, in accordance with an aspect of the present invention. 
     FIG. 4 illustrates another pointer adapted to store a local value associated with a reference count, in accordance with an aspect of the present invention. 
     FIG. 5 is a timing diagram, illustrating a reference count in a reference counted item and the local values associated with the reference count in referencing items, in accordance with the present invention. 
     FIG. 6 is another timing diagram, illustrating a reference count in a reference counted item and the local values associated with the reference count in referencing items, in accordance with the present invention. 
     FIG. 7 is another timing diagram, illustrating a reference count in a reference counted item and the local values associated with the reference count in referencing items, in accordance with the present invention. 
     FIG. 8 is another timing diagram, illustrating a reference count in a reference counted item and the local values associated with the reference count in referencing items, in accordance with the present invention. 
     FIG. 9 is a data flow diagram illustrating a sample data flow, in accordance with an aspect of the present invention. 
     FIG. 10 is a flow chart illustrating a method for acquiring a reference to a reference counted item, in accordance with an aspect of the present invention. 
     FIG. 11 is a flow chart further illustrating a method for releasing a reference to a reference counted item, in accordance with an aspect of the present invention. 
     FIG. 12 is a schematic block diagram of an exemplary operating environment for a system configured in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention is now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It may be evident, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate description of the present invention. 
     Referring initially to FIG. 1A, a system  10  for fast referencing a reference counted item  16  is illustrated. Both a fast referencing item  12  and non-fast referencing item  14  are illustrated. The reference counted item  16  may be, for example, a memory location, a data structure, and/or an object. The reference counted item  16  may be employed, for example, in association with a computer user profile. The profile may contain invariant data and variable data. The variable data may be, for example, the computer user&#39;s credentials concerning reading, writing and executing files. The variable data may be associated with a reference count in the reference counted item  16 . Although the variable data can change, if it is unlikely to change, then a local value associated with the count of the references to the variable data is suitable for caching in the fast referencing item  12 . The local value associated with the count of references to the variable data is thus available to other fast referencing items  12  and non-fast referencing items  14 . 
     Turning now to FIG. 1B, the fast referencing item  12  is illustrated including a fast reference count  33  (FRC), which holds a value representing F references, which are related to the count of references X stored in a reference count  31  in the reference counted item  16 . The FRC  33  can be created by a fast reference count creator  35 . For example, an operating system reference count manager may function as the fast reference count creator  35  and create the fast reference count  33 . The fast reference count creator  35  can be a computer related entity, either hardware, a combination of hardware and software, software, or software in execution. For example, the fast reference count creator  35  can be a process running on a processor, an operating system component, a processor, an object, an executable, a thread of execution, a program and a computer. The value of F is initially set to a value greater than the actual number of items referencing the reference counted item  16 , which facilitates subsequent referencing items to acquire references from the fast referencing item  12 . FIG. 1B also illustrates a new referencing item  15  that can attempt to acquire a reference to the reference counted item  16  from the fast referencing item  12  by employing the FRC  33 , thus mitigating problems associated with acquiring and releasing a lock associated with the reference counted item  16 . For example, the new referencing item  15  can utilize a count value from the FRC  33  in its attempt to reference the reference counted item  16 . Thus, by the FRC  33  having extra reference counts that may be employed by other referencing items, the FRC  33  facilitates quick referencing of the reference counted item  16  by the other referencing items. 
     Turning now to FIG. 2, the system  10  is illustrated in more detail. The reference counted item  16  includes a reference count  30 , which is a count of how many items are referring to the reference counted item  16 . The reference counted item  16  may also include other information, for example, data and/or methods  38 . The fast referencing item  12  maintains a pointer  34  to the reference counted item  16 , and also maintains a local value, (which can be part of the pointer), associated with the reference count  30 , which shall be referred to herein as a fast reference count  32  (FRC). In accordance with an aspect of the present invention, when creating the reference counted item  16 , the fast referencing item  12  acquires a lock to the reference counted item  16 , establishes the reference count  30  to a value greater than one, and releases the lock. Even though the fast referencing item  12  is only one item referring to the reference counted item  16 , by establishing the reference count  30  at a number greater than the actual number of items referencing the reference counted item  16 , the extra references acquired by the fast referencing item  12  may, under certain conditions, be acquired by other fast referencing items  12  and non-fast referencing items  14  (FIG. 1) without the requirement of acquiring and releasing a lock. One such condition exists when a fast referencing item  12  seeks to read but not change the values in the sub-data associated with the reference count  30 . Another such condition exists when a non-fast referencing item  14  seeks to read but not change the values in the sub-data associated with the reference count  30 . If either a fast referencing item  12  or a non-fast referencing item  14  seeks to change the sub-data associated with the reference count  30 , then those items will employ the conventional acquire lock, access, release lock method. 
     But when a subsequent acquiring item seeks to acquire a reference to enable reading data associated with the reference count  30 , then the acquiring item may employ a processor  37  to examine the FRC  32  in the fast referencing item  12  to determine whether any references are available to be acquired by the acquiring item. If one or more references are available to be acquired, then the acquiring item causes an atomic operation (e.g. InterlockedCompareExchange( )) to performed on the processor  37  to decrease the FRC  32  by the number of references acquired by the acquiring item, and establishes its own local reference count. Examining the FRC  32 , performing the atomic update operation and establishing a local reference count in the acquiring item are performed without the processor  37  acquiring and releasing a lock. Thus contention problems associated with conventional methods for acquiring a reference to the reference counted item  16  are mitigated. If the acquiring item is a fast referencing item  12 , then the acquiring item may in turn have an FRC  32  examined and be manipulated by other subsequent acquirers. The processor  37  may be a computer-related entity, either hardware, a combination of hardware and software, software, or software in execution. For example, a processor may be a process running on a microprocessor, a microprocessor, an object, an executable, a thread of execution, a program and a computer. By way of illustration, both an application running on a server and the server can be processors. 
     Turning now to FIG. 3, two exemplary methods for storing a fast reference count  52  (FRC) are illustrated. In the first method, a pointer  40 , consisting of N bits, and a variable  42 , consisting of X bits are employed. The pointer  40  holds the address of the reference counted item  16  (FIG.  1 ), while the variable  42  holds the fast reference count  52  (FRC). In a second method, a pointer  50  consisting of N bits, is partitioned into two parts, a pointer portion consisting of M bits and the FRC  52  part consisting of N-M bits. For example, the pointer  50  may consist of thirty-two bits, twenty-nine of which are allocated to storing the address of the reference counted item  16  (FIG. 1) while three are allocated to store the FRC  52 . Bits from the pointer  50  can be employed to store the FRC  52  when not all the N bits are required to store the address of the reference counted item  16  (FIG.  1 ). For example, if the reference counted item  16  is located in a memory area where data items are aligned on eight byte boundaries then three of the thirty-two bits are not required to store the address. The three available bits can thus be used to store the FRC  52 , with a value ranging from zero to seven. In FIG. 3, the three bits employed to store the FRC  52  are illustrated contiguous to each other, however, as is described below in connection with FIG. 4, the bits do not have to be contiguous. It is to be appreciated by one skilled in the art that although thirty-two bits and three bits are discussed above, that a greater or lesser number of bits may be employed in accordance with the present invention. 
     An advantage of the second method over the first method is that by using bits available in the pointer  50 , memory requirements can be reduced, and processing speed can be increased. For example, one memory lookup can be employed to resolve the address in the pointer  50  and to retrieve the FRC  52  versus two memory lookups in the first method. In either case, the FRC  52  may be examined without acquiring a lock by subsequent acquiring items to determine whether references are available to be acquired. If references are available, and the subsequent acquiring item seeks to read but not change the sub-data associated with the reference count  30  (FIG.  2 ), then the subsequent acquiring item may perform, without acquiring and releasing a lock, the atomic operation to change the FRC  52 . Thus, problems associated with contending for locks to acquire references to a reference counted item are mitigated. 
     FIG. 4 illustrates a pointer  68  adapted to store a fast reference count  60  (FRC) where the bits employed to store the FRC  60  are not contiguous. The pointer  68  can have N bits. If M bits are required to store the address of the reference counted item  16  (FIG.  1 ), then N-M bits are available to store the FRC  60 . In FIG. 4, the N-M bits, FRC AA1    62 , FRC A2    64  through FRC N-M    66  are distributed throughout the pointer  68 . Although the N-M bits are illustrated distributed left to right in the pointer  68 , it is to be appreciated by one skilled in the art that any suitable distribution of the N-M bits may be employed in the present invention. 
     FIG. 5 is a timing diagram, illustrating a reference count  90  in a reference counted item  72  as the reference count  90  is established and manipulated. A fast referencing item  70  establishes the reference counted item  72 . In establishing the reference counted item  72 , the fast referencing item  70  establishes the reference count  90  and a fast reference count  80 . The reference count  90 , the fast reference count  80 , and a fast reference count  100  are illustrated at four different times T 1 , T 2 , T 3  and T 4 . T 1  corresponds to the point in time where the fast referencing item  70  is created and in turn creates the reference counted item  72 . The fast referencing item  70  establishes a reference count  90   A1  with a value eight, indicating that eight items are referencing the reference counted item  72 . But at time T 1 , only one item is referencing the reference counted item  72 . Thus, seven references to the reference counted item  72  are available to be acquired by other items that seek to read, but not change, the sub-data associated with the reference counted object  72 . At time T 1 , a second fast referencing item  74  has not yet been created, and thus there is no defined value for the fast reference count  100   A1 . At time T 2 , the fast referencing item  74  is created. The fast referencing item  74  seeks to read, but not change the sub-data associated with the reference counted item  72 , and thus the fast referencing item  74  can attempt to acquire a reference from the fast referencing item  70 . The fast referencing item  74  examines the FRC  80   A1 , determines that references are available, and causes an atomic update of the FRC  80   A1  to reduce the FRC  80   A1  by the one reference that the fast referencing item  74  is acquiring. An atomic operation is required to facilitate no other concurrently acquiring item examining and changing the FRC  80   A1  concurrently with the fast referencing item  74 . When the atomic operation is completed, at time T 2 , the fast referencing item  70  has an FRC  80   A2  reduced to six, indicating that six references are available to be acquired, while the fast referencing item  74  has an FRC  100   A2  set to zero, indicating that it has no references available to be acquired. The reference count  90   A2  in the reference counted object  72  does not change since one reference is in use by the fast referencing item  70 , one reference is in use by the fast referencing item  74 , and six references are listed as available from the fast referencing item  70 , which adds up to the eight references indicated in the reference count  90   A2 . In an alternative example, the fast referencing item  74  can acquire more than one reference from the fast referencing item  70 , in which case the fast reference count  80   A2  is reduced by the number of references acquired by the fast referencing item  74 , and the fast reference count  100   A2  is set to one less than the number of references acquired, indicating the number of references available to be acquired from the fast referencing item  74 . After such an alternative acquisition, both the fast referencing item  70  and the fast referencing item  74  are available to be examined to determine whether either still has adequate references for other items to acquire. 
     At time T 3 , the fast referencing item  70  loses interest in the reference counted item  72 , and thus changes a reference count  90   A3  to one, indicating that the six “extra” references are no longer available, and that the one reference consumed by the fast referencing item  70  is no longer in use. The fast referencing item  70  sets an FRC  80   A3  to a null value, indicating that the fast referencing item  70  is no longer referencing the reference counted item  72 . The value one in the reference count  90   A3  correctly indicates that one item, the fast referencing item  74  is referring to the reference counted item  72 . 
     At time T 4 , the fast referencing item  74  loses interest in the reference counted item  72 , and thus changes a reference count  90   A4  to zero, indicating that no items are referencing the reference counted object  72 . The zero in the reference count  90   A4  indicates that the memory associated with the reference counted item  72  can be reclaimed by, for example, a garbage collection process. The fast referencing item  74  sets an FRC  100   A4  to a null value, indicating that the fast referencing item  74  is no longer referencing the reference counted item  72 . 
     It is to be appreciated by one skilled the art that although the fast referencing item  70  initially established a count of eight in the reference counted item  72 , that any suitable value greater than one may be established in the reference counted item  72  to facilitate subsequent acquiring items acquiring a reference to the reference counted item  72  without acquiring and releasing a lock. Thus, problems associated with contention for a lock are mitigated. It is to be further appreciated that the fast referencing item  74  may acquire more than one reference from the fast referencing item  70 . 
     FIG. 6 is a timing diagram, illustrating a reference count  130  in a reference counted item  112  as the reference count  130  is established and manipulated. A fast referencing item  114  establishes the reference counted item  112 . In establishing the reference counted item  112 , the fast referencing item  114  establishes the reference count  130  and a fast reference count  120 . The reference count  130 , the fast reference count  120 , and a non-fast reference count  140  are illustrated at four different times T 1 , T 2 , T 3  and T 4 . T 1  corresponds to the point in time where the fast referencing item  114  is created and in turn creates the reference counted item  112 . The fast referencing item  114  establishes a reference count  130   A1  with a value eight, indicating that eight items are referencing the reference counted item  112 . But at time T 1 , only one item is referencing the reference counted item  112 . Thus, seven references to the reference counted item  112  are available to be acquired by other items that seek to read, but not change, the sub-data associated with the reference counted object  112 . At time T 1 , a non-fast referencing item  116  has not yet been created, and thus there is no defined value for a non-fast reference count  140   A1 . 
     At time T 2 , the non-fast referencing item  116  is created. The non-fast referencing item  116  seeks to read, but not change the sub-data associated with the reference counted item  112 , and thus the non-fast referencing item  116  attempts to acquire a reference from the fast referencing item  114 . The non-fast referencing item  116  examines an FRC  120   A1 , determines that references are available, and causes an atomic update of the FRC  120   A1  to reduce the FRC  120   A1  by the one reference that the non-fast referencing item  116  is acquiring. An atomic operation is required to facilitate no other concurrently acquiring item examining and changing the FRC  120   A1  concurrently with the non-fast referencing item  116 . When the atomic operation is completed, at time T 2 , the fast referencing item  114  has an FRC  120   A2  reduced to six, indicating that six references are available to be acquired, while the non-fast referencing item  116  has an FRC  140   A2  set to one, indicating that it is consuming a reference. The non-fast referencing item  116  can not be used to acquire references from and thus its non-fast reference count  140  does not indicate that references are available, but rather that it is consuming a reference. A reference count  130   A2  in the reference counted object  112  does not change since one reference is in use by the fast referencing item  114 , one reference is in use by the non-fast referencing item  116 , and six references are listed as available from the fast referencing item  114 , which adds up to the eight references indicated in the reference count  130   A2 . 
     At time T 3 , the fast referencing item  114  loses interest in the reference counted item  112 , and thus changes a reference count  130   A3  to one, indicating that the six “extra” references are no longer available, and that the one reference consumed by the fast referencing item  114  is no longer in use. The fast referencing item  114  sets an FRC  120   A3  to a null value, indicating that the fast referencing item  114  is no longer referencing the reference counted item  112 . The value one in a reference count  130   A3  correctly indicates that one item, the non-fast referencing item  116  is referring to the reference counted item  112 . 
     At time T 4 , the non-fast referencing item  116  loses interest in the reference counted item  112 , and thus changes a reference count  130   A4  to zero, indicating that no items are referencing the reference counted object  72 . The zero in reference count  130   A4  indicates that the memory associated with the reference counted item  112  can be reclaimed by, for example, a garbage collection process. The non-fast referencing item  116  sets an FRC  140   A4  to a null value, indicating that the non-fast referencing item  116  is no longer referencing the reference counted item  112 . 
     It is to be appreciated by one skilled the art that although the fast referencing item  114  initially established a count of eight in the reference counted item  112 , that any suitable value greater than one may be established in the reference counted item  112  to facilitate subsequent acquiring items acquiring a reference to the reference counted item  112  without acquiring and releasing a lock. Thus, problems associated with contention for a lock are mitigated. 
     FIG. 7 is a timing diagram, illustrating a reference count  170  in a reference counted item  152  as the reference count  170  is established and manipulated. A fast referencing item  150  establishes the reference counted item  152 . In establishing the reference counted item  152 , the fast referencing item  150  establishes the reference count  170  and a fast reference count  160 . The reference count  170 , the fast reference count  160 , and a non-fast reference count  180  are illustrated at four different times T 1 , T 2 , T 3  and T 4 . T 1  corresponds to the point in time where the fast referencing item  150  is created and in turn creates the reference counted item  152 . The fast referencing item  150  establishes a reference count  170   A1  with a value eight, indicating that eight items are referencing the reference counted item  152 . But at time T 1 , only one item is referencing the reference counted item  152 . Thus, seven references to the reference counted item  152  are available to be acquired by other items that seek to read, but not change, the sub-data associated with the reference counted object  152 . At time T 1 , a non-fast referencing item  154  has not yet been created, and thus there is no defined value for a non-fast reference count  160   A1 . At time T 2 , the non-fast referencing item  154  is created. The non-fast referencing item  154  seeks to read, but not change the sub-data associated with the reference counted item  152 , and thus the non-fast referencing item  154  can attempt to acquire a reference from the fast referencing item  150 . The non-fast referencing item  154  examines an FRC  160   A1 , determines that references are available, and causes an atomic update of the FRC  160   A1  to reduce the FRC  160   A1  by the one reference that the non-fast referencing item  154  is acquiring. An atomic operation is required to facilitate no other concurrently acquiring item examining and changing the FRC  160   A1  concurrently with the non-fast referencing item  154 . When the atomic operation is completed, at time T 2 , the fast referencing item  150  has an FRC  160   A2  reduced to six, indicating that six references are available to be acquired, while the non-fast referencing item  154  has its non-fast reference count  160   A2  set to one, indicating that it is consuming a reference. The non-fast referencing item  154  can not be used to acquire references from and thus its non-fast reference count  160  does not indicate that references are available, but rather that it is consuming a reference. A reference count  170   A2  in the reference counted object  152  does not change since one reference is in use by the fast referencing item  150 , one reference is in use by the non-fast referencing item  154 , and six references are listed as available from the fast referencing item  150 , which adds up to the eight references indicated in the reference count  170   A2 . 
     At least two methods are available for the non-fast referencing item  154  to release acquired references when it loses interest in the reference counted item  170 . In a first method, the non-fast referencing object  154  de-references the reference counted item  152  directly. Thus, at time T 31 , the non-fast referencing item  154  loses interest in the reference counted item  152 , and changes a reference count  170   A3  to seven, indicating that the one reference consumed by non-the fast referencing item  154  is no longer in use. The non-fast referencing item  154  sets an FRC  160   A3  to a null value, indicating that the non-fast referencing item  154  is no longer referencing the reference counted item  152 . The value seven in the reference count  170   A3  correctly indicates that one item, the fast referencing item  150  is referring to the reference counted item  152  and that it has six “extra” references still available for acquisition by other items. 
     In another method the non-fast referencing item  154  may return the reference it acquired from the fast referencing item  150 . Thus at time T 32  the non-fast referencing object performs an atomic operation to increase a fast reference count  160   A4  to seven, indicating that it has had the reference acquired by the non-fast referencing item  154  returned and that seven references are again available for acquisition. 
     Similarly, at least two methods are available for a fast referencing item to de-reference the reference counted item  152 . In a first method, the fast referencing item can reduce the fast reference count  170  by the number of references released by the fast referencing item. In a second method, the fast referencing item can return the number of references acquired from another fast referencing item, leaving the reference count  170  unchanged. Before returning the acquired references to the fast referencing item from which they were acquired, the returning item will determine that the fast referencing item from which the references were acquired still exists and is available to have the references returned. 
     It is to be appreciated by one skilled the art that although the fast referencing item  150  initially established a count of eight in the reference counted item  152 , that any suitable value may be established in the reference counted item  152  to facilitate subsequent acquiring items acquiring a reference to the reference counted item  152  without acquiring and releasing a lock. Thus, problems associated with contention for a lock are mitigated. 
     Turning now to FIG. 8, another timing diagram illustrating a reference counted item  202  is provided. At time T 1 , a fast referencing item  200  is created and establishes the reference counted item  202 . The fast referencing item  200  sets a reference count  220   A1  to eight, indicating that the fast referencing item  200  has acquired eight references to the reference counted item  202 . At time T 1 , a fast referencing item  204  has not yet been created, and thus there is no value for a fast reference count  230   A1 . At time T 1 , the fast referencing item  200  sets a fast reference count  223   A1  to seven, indicating that it has seven references available to be acquired. 
     At time T 2 , which may be some period of time later than time T 1 , (e.g. many acquisitions and/or releases may have occurred), the fast referencing item  204  is created. The fast referencing item  204  examines the fast reference count  223 , and determines it can acquire a reference from the fast reference item  200 . In performing the atomic operation to reduce the fast reference count  223 , the fast reference object  204  determines that it has forced a fast reference count  223   A2  to zero. Thus, the fast referencing object  204  performs additional processing, to determine if additional references to the reference counted item  202  may be acquired. If more references may be acquired, then the fast referencing item  204  may acquire those references and keep them for itself or assign them to the fast referencing item  200 . In FIG. 8, the fast referencing item  204  determines that references are available to the reference counted item  202  by examining a reference count  220   A2 . Since the reference count  220   A2  is less than the maximum number of references allowed to the reference counted item  202 , the fast referencing item  204  acquires a lock, changes the reference count  220   A3  to eight at T 3  and assigns the additional references to the fast reference item  200  where a fast reference count  223   A3  is increased to six. At time T 4 , the fast referencing item  204  loses interest in the reference counted item  202  and thus returns its reference to the fast referencing item  200 , increasing a fast reference count  223   A4  to seven. 
     Although the fast referencing item  204  acquired six additional references to the reference counted item  202 , it is to be appreciated by one skilled in the art that a greater or lesser number of references could have been acquired by the fast referencing item  204  in accordance with the present invention. Similarly, it is to be appreciated that although the fast referencing item  204  assigned six of the additionally acquired references to the fast referencing item  200 , a lesser number can be assigned, and a greater number can be retained. 
     Turning now to FIG. 9, a sample data flow through an aspect of the present invention is illustrated. A fast reference item  300  creates a reference counted item  302 . The reference counted item  302  has a reference count  308  associated with it. A copy of the reference count  304  is passed to the fast reference item  300 . The fast reference item  300  creates and stores a local value (e.g. a fast reference count) associated the reference count  304  in a fast ref data store  306 . The fast ref count data store  306  can contain a value different from the value stored in the ref count data store  308 . Other fast referencing items  310  may seek to acquire a reference to the reference counted item  302 . 
     In accordance with an aspect of the present invention, the fast referencing items  310  examine the fast reference count stored in the ref count  306  data store. If the fast referencing items  310  determine that references are available to be acquired, then the fast referencing items  310  can employ an atomic operation (e.g. InterlockedCompareExchange( )) to reduce the number of available references in the fast ref count  306  data store by an amount equal to the number of references acquired by the fast referencing items  310 . The fast referencing items  310  store a value associated with the number of references acquired in a fast ref count  314  data store. The fast referencing items  310  may in turn be examined for the availability of references and may have their “extra” references acquired. 
     When the fast referencing items  310  are done with the acquired references, the fast referencing items  310  may employ an atomic operation to increase the number of available references in the fast ref count  306  data store by an amount equal to the number of references released by the fast referencing items  310 . The fast referencing items  310  may also acquire a lock, return the acquired references to the reference counted object  302  by decreasing the reference count stored in the ref count  308  data store, and release the lock. 
     The fast referencing items  310  may also determine that by acquiring one or more references from the fast referencing item  300 , that the available references stored in the fast ref count  306  data store have been exhausted. The fast referencing items  310  may thus attempt to acquire additional references to the reference counted item  302  and either retain the additional references for themselves, or assign the additional references to the fast referencing item  300 . 
     Non-fast referencing items  320  may also seek to acquire a reference to the reference counted item  302 . In accordance with an aspect of the present invention, the non-fast referencing items  320  examine the count stored in the fast ref count  306  data store. If the non-fast referencing items  320  determine that references are available to be acquired, then the non-fast referencing items  320  can employ an atomic operation (e.g. InterlockedCompareExchange( )) to reduce the number of available references in the fast ref count  306  data store by an amount equal to the number of references acquired by the non-fast referencing items  320 . The non-fast referencing items  320  may also directly de-reference the reference counted item  302  or return the acquired references to the fast referencing item  300 . 
     Although one acquiring fast referencing item  310  and one acquiring non-fast referencing item  320  are illustrated, it is to be appreciated by one skilled in the art that a greater or lesser number of fast referencing items and/or non-fast referencing items may be employed in accordance with the present invention. 
     Throughout the discussion associated with FIGS. 1 through 8, the term “item” has been employed (e.g. reference counted item, fast referencing item, non-fast referencing item). It is to be appreciated by one skilled in the art that the meaning of the term “item” as so employed can include, but is not limited to, memory locations, data structures, objects, processes and/or threads of executions. 
     In view of the exemplary systems shown and described above, a methodology, which may be implemented in accordance with the present invention, will be better appreciated with reference to the flow diagrams of FIG.  10  and FIG.  11 . While, for purposes of simplicity of explanation, the methodologies of FIG.  10  and FIG. 11 are shown and described as a series of steps, it is to be understood and appreciated that the present invention is not limited by the order of the steps, as some steps can, in accordance with the present invention, occur in different orders and/or concurrently with other steps from that shown and described herein. Moreover, not all illustrated steps may be required to implement a methodology in accordance with the present invention. 
     Turning now to FIG. 10, a method for acquiring a reference to a reference counted item is flow-charted. At step  400 , general initializations are performed. For example, a fast referencing item may be created, a reference counted object may be created, a reference count may established in the reference counted object, and a local value associated with the reference count (e.g. a fast reference count (FRC)) may be established. At step  410  an item seeking to acquire a reference to the reference counted item of step  400  examines the FRC to determine whether the fast referencing item of step  400  has any references available for acquisition. 
     At step  420 , a determination is made concerning whether the FRC is greater than a pre-determined threshold. If at step  420  the determination is NO, then at step  430  a conventional method for acquiring a reference employing locking, accessing and unlocking is performed. At step  440 , a determination is made concerning whether there are any more acquirers? If the determination at step  440  is YES, then control returns to step  410 , otherwise the method concludes. If the determination at step  420  is YES, then at step  450  a determination is made concerning whether the acquiring item is a fast referencing item? If the determination at step  450  is NO, then at step  460  the non-fast referencing item acquires one reference to the reference counted item of step  400 , employing an atomic operation to manipulate the FRC, after which control passes to step  440 . If the determination at step  450  is YES, then at step  470  the acquiring fast referencing item acquires I references, I being an integer. In step  470  an atomic operation is employed to manipulate the FRC of the item from which the references were acquired. 
     At step  480  a determination is made concerning whether the acquisition of step  470  forced the FRC in the item from which the references were acquired to zero. If the determination at step  480  is NO, then control passes to step  440 . But if the determination at step  480  is YES, then at step  490  the acquiring fast reference item may attempt to fix up the FRC of the fast referencing item from which the references were acquired. For example, the acquiring fast referencing item may examine the reference count of the reference counted item of step  400  and determine whether additional references are available. If such additional references are available, then the acquiring fast reference item can use a lock, access and unlock method to acquire the additional references and can assign the additional references to the fast referencing item whose FRC was forced to zero. Alternatively, the acquiring fast referencing item can retain the additional references, which will subsequently be available for acquisition by other acquiring items. 
     Turning now to FIG. 11 a method for releasing one or more references to a reference counted item is flow-charted. At step  500 , a determination is made concerning whether the item releasing the one or more references is a fast referencing item. If the determination at step  500  is YES, then at step  510  a determination is made concerning whether the releasing item wants to return the one or more references to the fast referencing item from which it acquired the references. If the determination at step  510  is NO, then at step  520  the releasing item de-references the reference counted item directly, after which control passes to step  530 . At step  530  a determination is made concerning whether there are any more releasing items. If the determination at step  530  is YES, then control passes to step  500 , otherwise the method concludes. If at step  510  the determination was YES, then at step  540  a determination is made concerning whether the fast referencing item from which the references were acquired still exists. If the determination at step  540  is NO, then control passes to step  520 . Otherwise, if the determination at step  540  is YES, then at step  550  the returning item returns I references, I being an integer greater than or equal to one. The returning item may return all or less than all of the references it acquired from the fast referencing item. At step  560 , a determination is made concerning whether the releasing item has any references to the reference counted item left. If the determination is NO, then the releasing item no longer references the reference counted item and at step  570  sets the releasing item&#39;s FRC to a NULL value, indicating that it no longer references the reference counted item, after which control passes to step  530 . If the determination at step  560  is YES, then the releasing item still references the reference counted item, and thus control passes to step  530 . 
     If the determination at step  500  was NO, that the releasing item is not a fast referencing item, and at step  580  a determination is made concerning whether the releasing item wants to return its reference to the fast referencing item from which it acquired the reference. If the determination at step  580  is NO, then at step  590  the releasing item de-references the reference counted item directly, after which control passes to step  530 . If at step  580  the determination was YES, then at step  600  a determination is made concerning whether the fast referencing item from which the references were acquired still exists. If the determination at step  600  is NO, then control passes to step  590 . Otherwise, if the determination at step  600  is YES, then at step  610  the returning item returns its reference to the fast referencing item from which it acquired the reference, after which control passes to step  530 . 
     With reference to FIG. 12, an exemplary environment  710  for implementing various aspects of the invention includes a computer  712 , including a processing unit  714 , a system memory  716 , and a system bus  716  that couples various system components including the system memory  716  to the processing unit  714 . The processing unit  714  may be any of various commercially available processors. Dual microprocessors and other multi-processor architectures also can be used as the processing unit  714 . 
     The system bus  716  may be any of several types of bus structure including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of commercially available bus architectures. The system memory  716  includes read only memory (ROM)  720  and random access memory (RAM)  722 . A basic input/output system (BIOS), containing the basic routines that help to transfer information between elements within the computer  712 , such as during start-up, is stored in ROM  720 . 
     The computer  712  further includes a hard disk drive  724 , a magnetic disk drive  726 , e.g., to read from or write to a removable disk  728 , and an optical disk drive  730 , e.g. for reading a CD-ROM disk  732  or to read from or write to other optical media. The hard disk drive  724 , magnetic disk drive  726 , and optical disk drive  730  are connected to the system bus  716  by a hard disk drive interface  734 , a magnetic disk drive interface  736 , and an optical drive interface  738 , respectively. The drives and their associated computer-readable media provide nonvolatile storage of data, data structures, computer-executable instructions, etc. for the computer  712 , including for the storage of broadcast programming in a suitable digital format. Although the description of computer-readable media above refers to a hard disk, a removable magnetic disk and a CD, it should be appreciated by those skilled in the art that other types of media which are readable by a computer, such as zip drives, magnetic cassettes, flash memory cards, digital video disks, Bernoulli cartridges, and the like, may also be used in the exemplary operating environment, and further that any such media may contain computer-executable instructions for performing the methods of the present invention. 
     A number of program modules may be stored in the drives and RAM  722 , including an operating system  740 , one or more application programs  742 , other program modules  744 , and program data  746 . The operating system  740  in the illustrated computer is, for example, the “Microsoft® Windows® NT” operating system, although it is to be appreciated that the present invention may be implemented with a variety of commercially available operating systems or combinations of operating systems. 
     A user may enter commands and information into the computer  712  through a keyboard  748  and a pointing device, such as a mouse  750 . Other input devices (not shown) may include a microphone, an IR remote control, a joystick, a game pad, a satellite dish, a scanner, or the like. These and other input devices are often connected to the processing unit  714  through a serial port interface  752  that is coupled to the system bus  716 , but may be connected by other interfaces, such as a parallel port, a game port, a universal serial bus (“USB”), an IR interface, etc. A monitor  754  or other type of display device is also connected to the system bus  716  via an interface, such as a video adapter  756 . In addition to the monitor  754 , a computer  712  typically includes other peripheral output devices (not shown), such as speakers, printers etc. 
     The computer  712  may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer(s)  758 . The remote computer(s)  758  may be a workstation, a server computer, a router, a personal computer, microprocessor based entertainment appliance a peer device or other common network node, and typically includes many or all of the elements described relative to the computer  712 , although, for purposes of brevity, only a memory storage device  760  is illustrated. The logical connections depicted include a local area network (LAN)  762  and a wide area network (WAN)  764 . Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet. 
     When used in a LAN networking environment, the computer  712  is connected to the local network  762  through a network interface or adapter  766 . When used in a WAN networking environment, the computer  712  typically includes a modem  768 , or is connected to a communications server on the LAN, or has other means for establishing communications over the WAN  764 , such as the Internet. The modem  768 , which may be internal or external, may be connected to the system bus  716  via the serial port interface  752  to enable communications, for example, via POTS. In an alternative embodiment, the modem  768 , which may be internal or external, may be connected to the system bus  716  via the network adaptor  766  to enable communications, for example, via DSL and/or modem. In a networked environment, program modules depicted relative to the computer  712 , or portions thereof, may be stored in the remote memory storage device  760 . It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used. 
     What has been described above includes examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art may recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted as a transitional word in a claim.