Abstract:
A computer implemented method for reducing communication signaling protocol latency. An acceptable level of latency is specified. Automatic memory management activities are monitored based on specified parameters to calculate a level of activity that determines whether a reduction of activity is required.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a data processing system. More specifically, the present invention relates to a computer implemented method, computer program product and data processing system for reducing communication signaling protocol latency. 
   2. Description of the Related Art 
   The session initiation protocol(SIP) is being implemented in the Java language, for example, SIP container in WebSphere, and being used by service providers. Session initiation protocol (SIP) is an Internet signaling protocol which has many uses, such as Voice over IP (VoIP). Session initiation protocol (SIP) can establish sessions for features such as audio/videoconferencing, interactive gaming, and call forwarding to be deployed over networks thus enabling service providers to integrate basic telephony services with Web, e-mail, and chat services. Session initiation protocol (SIP) is an example of a communication signaling protocol. Session initiation protocol (SIP) has quality of service (QoS) requirements. Customers are concerned about end-to-end latency. In particular, customers would like deterministic latency and they are willing to reduce throughput to get more deterministic latency. 
   A problem in providing deterministic latency in a virtual machine environment, such as Java, C#, Lisp, Perl, and so forth, is that garbage collection events occur that stop all application processing for a period of time. Garbage collection is a form of automatic memory management. Memory management is the act of managing computer memory. In its simpler forms memory management involves providing ways to allocate portions of memory to programs at their request and free the portions of memory back to the system for reuse when the portions of memory are no longer needed. A garbage collector or collector attempts to reclaim garbage, or memory used by objects that will never again be accessed or mutated by the application. Memory can be allocated and used, and the garbage collection process will automatically free any chunks of memory that are no longer referenced. Typically, garbage collection involves the automatic reclamation of dynamically allocated objects that are no longer accessible. This ‘stop the world’ garbage collection time is based on the amount of heap used and the number of objects created. 
   One approach to solving this ‘stop the world’ garbage collection time is to oversize the number of CPU&#39;s used by the system, which is not very cost effective. Another solution is to measure an application&#39;s garbage collection activity and tune the garbage collection algorithm. However, this solution can only go so far. Another solution is to have a scheduled, periodic thread that performs garbage collection activities. An input to this thread is the frequency and length at which the periodic garbage collection thread operates. 
   However, a concern still remains that the workload could over-run the capacity of the periodic garbage collection thread when the input rate spikes and the object creation rate exceeds the rate at which the periodic garbage collection thread can perform garbage collection activities. It is desirable to solve this problem in a manner that would also supplement existing garbage collection algorithms, that is generational garbage collection, because the existing algorithms do have a low priority, background thread that performs garbage collection activities. 
   BRIEF SUMMARY OF THE INVENTION 
   Exemplary embodiments describe a computer implemented method, a computer program product and a data processing system for reducing communication signaling protocol latency. Automatic memory management activities are optimized based on a specified level of latency. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a pictorial representation of a network of data processing systems in which exemplary aspects may be implemented; 
       FIG. 2  is a block diagram of a data processing system in which exemplary aspects may be implemented; 
       FIG. 3  is a block diagram of components for reducing communication signaling protocol latency in accordance with an exemplary embodiment; and 
       FIG. 4  is a flowchart illustrating the operation of reducing session initiation protocol latency in a Java environment in accordance with an exemplary embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-2  are provided as exemplary diagrams of data processing environments in which embodiments may be implemented. It should be appreciated that  FIGS. 1-2  are only exemplary and are not intended to assert or imply any limitation with regard to the environments in which aspects or embodiments may be implemented. Many modifications to the depicted environments may be made without departing from the spirit and scope. 
   With reference now to the figures,  FIG. 1  depicts a pictorial representation of a network of data processing systems in which aspects may be implemented. Network data processing system  100  is a network of computers in which exemplary embodiments may be implemented. Network data processing system  100  contains network  102 , which is the medium used to provide communications links between various devices and computers connected together within network data processing system  100 . Network  102  may include connections, such as wire, wireless communication links, or fiber optic cables. 
   In the depicted example, server  104  and server  106  connect to network  102  along with storage unit  108 . In addition, clients  110 ,  112 , and  114  connect to network  102 . These clients  110 ,  112 , and  114  may be, for example, personal computers or network computers. In the depicted example, server  104  provides data, such as boot files, operating system images, and applications to clients  110 ,  112 , and  114 . Clients  110 ,  112 , and  114  are clients to server  104  in this example. Network data processing system  100  may include additional servers, clients, and other devices not shown. 
   In the depicted example, network data processing system  100  is the Internet with network  102  representing a worldwide collection of networks and gateways that use the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols to communicate with one another. At the heart of the Internet is a backbone of high-speed data communication lines between major nodes or host computers, consisting of thousands of commercial, government, educational and other computer systems that route data and messages. Of course, network data processing system  100  also may be implemented as a number of different types of networks, such as for example, an intranet, a local area network (LAN), or a wide area network (WAN).  FIG. 1  is intended as an example, and not as an architectural limitation for different embodiments. 
   With reference now to  FIG. 2 , a block diagram of a data processing system is shown in which aspects may be implemented. Data processing system  200  is an example of a computer, such as server  104  or client  110  in  FIG. 1 , in which computer usable code or instructions implementing the processes for embodiments may be located. 
   In the depicted example, data processing system  200  employs a hub architecture including north bridge and memory controller hub (NB/MCH)  202  and south bridge and input/output (I/O) controller hub (ICH)  204 . Processing unit  206 , main memory  208 , and graphics processor  210  are connected to north bridge and memory controller hub  202 . Graphics processor  210  may be connected to north bridge and memory controller hub  202  through an accelerated graphics port (AGP). 
   In the depicted example, local area network (LAN) adapter  212  connects to south bridge and I/O controller hub  204 . Audio adapter  216 , keyboard and mouse adapter  220 , modem  222 , read only memory (ROM)  224 , hard disk drive (HDD)  226 , CD-ROM drive  230 , universal serial bus (USB) ports and other communications ports  232 , and PCI/PCIe devices  234  connect to south bridge and I/O controller hub  204  through bus  238  and bus  240 . PCI/PCIe devices may include, for example, Ethernet adapters, add-in cards and PC cards for notebook computers. PCI uses a card bus controller, while PCIe does not. ROM  224  may be, for example, a flash binary input/output system (BIOS). 
   Hard disk drive  226  and CD-ROM drive  230  connect to south bridge and I/O controller hub  204  through bus  240 . Hard disk drive  226  and CD-ROM drive  230  may use, for example, an integrated drive electronics (IDE) or serial advanced technology attachment (SATA) interface. Super I/O (SIO) device  236  may be connected to south bridge and I/O controller hub  204 . 
   An operating system runs on processing unit  206  and coordinates and provides control of various components within data processing system  200  in  FIG. 2 . As a client, the operating system may be a commercially available operating system such as Microsoft® Windows® XP (Microsoft and Windows are trademarks of Microsoft Corporation in the United States, other countries, or both). An object-oriented programming system, such as the Java™ programming system, may run in conjunction with the operating system and provides calls to the operating system from Java programs or applications executing on data processing system  200  (Java is a trademark of Sun Microsystems, Inc. in the United States, other countries, or both). 
   As a server, data processing system  200  may be, for example, an IBM eServer™ pSeries® computer system, running the Advanced Interactive Executive (AIX®) operating system or LINUX operating system (eServer, pSeries and AIX are trademarks of International Business Machines Corporation in the United States, other countries, or both while Linux is a trademark of Linus Torvalds in the United States, other countries, or both). Data processing system  200  may be a symmetric multiprocessor (SMP) system including a plurality of processors in processing unit  206 . Alternatively, a single processor system may be employed. 
   Instructions for the operating system, the object-oriented programming system, and applications or programs are located on storage devices, such as hard disk drive  226 , and may be loaded into main memory  208  for execution by processing unit  206 . The processes for embodiments are performed by processing unit  206  using computer usable program code, which may be located in a memory such as, for example, main memory  208 , read only memory  224 , or in one or more peripheral devices  226  and  230 . 
   Those of ordinary skill in the art will appreciate that the hardware in  FIGS. 1-2  may vary depending on the implementation. Other internal hardware or peripheral devices, such as flash memory, equivalent non-volatile memory, or optical disk drives and the like, may be used in addition to or in place of the hardware depicted in  FIGS. 1-2 . Also, the processes may be applied to a multiprocessor data processing system. 
   In some illustrative examples, data processing system  200  may be a personal digital assistant (PDA), which is configured with flash memory to provide non-volatile memory for storing operating system files and/or user-generated data. 
   A bus system may be comprised of one or more buses, such as bus  238  or bus  240  as shown in  FIG. 2 . Of course the bus system may be implemented using any type of communications fabric or architecture that provides for a transfer of data between different components or devices attached to the fabric or architecture. A communications unit may include one or more devices used to transmit and receive data, such as modem  222  or network adapter  212  of  FIG. 2 . A memory may be, for example, main memory  208 , read only memory  224 , or a cache such as found in north bridge and memory controller hub  202  in  FIG. 2 . The depicted examples in  FIGS. 1-2  and above-described examples are not meant to imply architectural limitations. For example, data processing system  200  also may be a tablet computer, laptop computer, or telephone device in addition to taking the form of a PDA. 
   An exemplary embodiment provides reducing communication signaling protocol latency. Latency, which is a synonym for delay, is an expression of how much time it takes for a packet of data to get from one designated point to another designated point. In an exemplary embodiment, a load balancer monitors the rate at which heap is being consumed, objects are being generated, average garbage collection time, and the rate of garbage collection activity that a background garbage collection thread is doing. Heap is a large block of process memory typically managed by a runtime library. Application memory requests are satisfied from the heap and its runtime routines. The load balancer has a filter that will throttle the acceptance of requests if the garbage collection background thread either cannot keep up with specified parameters or the average or maximum garbage collection time is above or approaching a certain threshold. Throttle means to regulate or slow down a sender. In the present exemplary embodiment, throttle means to slow the rate of acceptance of requests. This throttling of request acceptance trades off throughput for achieving and maintaining deterministic latency. 
   Exemplary embodiments function in an on demand router (ODR), which includes a load balancer. Another exemplary embodiment functions with the current J9 generational garbage collection. 
   Turning back to the figures,  FIG. 3  is a block diagram of components reducing communication signaling protocol latency in accordance with an exemplary embodiment. Exemplary embodiments may be implemented in any virtual machine based language that has garbage collection. Other exemplary embodiments may be implemented in any load balancing environment. 
   WebSphere application server (WAS) SIP cluster  300  is comprised of on demand router  302  in front and three hardware (h/w) servers SIP server  304 ,  306 , and  308 , that have two WebSphere application servers, app svr  310 ,  312 ,  314 ,  316 ,  318 , and  320 , running on each h/w server. The WebSphere application server is a world class J2EE compliant application server platform that supports dynamic content and Java web applications. The WebSphere application server combines enterprise-level data and transactional services with business information to provide a robust web site infrastructure. The applications are session initiation protocol related. Applications that are session initiation protocol (SIP) related include those applications that only use session initiation protocol (SIP) as well as applications that may have a small use of session initiation protocol (SIP) but are based on other technologies as well. Optionally, WAS SIP cluster  300  includes a dedicated replication server  322 . 
   The load balancer  324 , which is part of on demand router  302 , maintains a running average and other statistics of the following parameters:
         T—Time to perform a garbage collection activity that ‘stops the world’.   Hp—Total heap allocation per user request.   Op—Total number of objects created per user request.   Ot—Rate of object reclamation by the garbage collection thread.   Ht—Rate of heap reclamation by the garbage collection thread.   R—Rate of input requests.   P—Hardware platform characteristics (e.g., number of CPU&#39;s, type of CPU).   U—Performance measurements of the hardware server upon which the application server is located (e.g., CPU utilization).       

   The input parameters to the filter are as follows:
         Lh—acceptable latency due to slowness of heap reclamation, which may be either an average or maximum amount.   Lo—acceptable latency due to slowness of object reclamation, which may be either an average or maximum amount.       

   There are two functions that need to be developed. The two functions are usually developed by empirical measurements, along with platform scaling information. The functions may be, for example, a lookup table. The first function, function F 1 , returns the expected garbage collection latency due to the heap that needs to be scanned when a garbage collection event occurs. The first function takes as input the rate at which the heap is being consumed by input requests, the rate at which it is being reclaimed by the garbage collection thread, the hardware platform characteristics, and the environmental performance measurements on that hardware (h/w) server, for example, CPU utilization that is not due to the application server and is outside the Java virtual machine&#39;s (JVM&#39;s) control. 
   The second function, function F 2 , returns the expected garbage collection latency due to the objects not gathered when a garbage collection event is triggered. The second function takes as input the rate at which the objects are created by the input requests, the rate at which objects are being reclaimed by the garbage collection thread, the hardware platform characteristics, and the environmental performance measurements on that h/w server, for example, CPU utilization that is not due to the application server and is outside the Java virtual machine&#39;s (JVM&#39;s) control. 
   The algorithm for optimizing the garbage collection activity for each application server becomes: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               for each application server 
             
             
                 
                 If[F1(R*Hp,P,U,Ht)&lt;Lh]&amp;&amp;[F2(R*Op,P,U,Ot)&lt;LO] 
             
             
                 
                 then 
             
             
                 
                   send user request to application server 
             
             
                 
                 else 
             
             
                 
                 if each application server in the cluster has 
             
             
                 
                 been tried without success 
             
             
                 
                   then 
             
             
                 
                     reject the request 
             
             
                 
                   else 
             
             
                 
                     next application server 
             
             
                 
                   endif 
             
             
                 
                 endif 
             
             
                 
               endfor 
             
             
                 
                 
             
           
        
       
     
   
   In an exemplary embodiment the two functions are combined into a single implementation. 
   In session initiation protocol (SIP), there are two types of messages that may be important to refuse in the case where the servers are too busy. One message type that may be refused is any session initiation protocol (SIP) message which is an indiscriminate message, or a message that applies to all sessions. Another type of message that may be refused is a session initiation protocol (SIP) message which begins a new session initiation protocol (SIP) session. 
   In the case of a refused indiscriminate message, the message will be retransmitted after some timer period, which will introduce a delay. In the case of a refused session initiation protocol (SIP) message that begins a new session initiation protocol (SIP) session, any sessions which are active will still receive their messages so they will not experience any delay but any new sessions will either be outright rejected or need to wait for the protocol retransmission. 
   In an exemplary embodiment, the algorithm for optimizing garbage collection activity for each application server, which also takes into account the variations mentioned above may be implemented as: 
   
     
       
             
             
           
         
             
                 
                 
             
           
           
             
                 
               for each application server 
             
             
                 
                 If bypass condition=false and 
             
             
                 
                 [F1(R*Hp,P,U,Ht)&lt;Lh]&amp;&amp;[F2(R*Op,P,U,Ot)&lt;LO] 
             
             
                 
                 then 
             
             
                 
                   send user request to application server 
             
             
                 
                 else 
             
             
                 
                 if each application server in the cluster has 
             
             
                 
                 been tried without success 
             
             
                 
                   then 
             
             
                 
                     reject the request 
             
             
                 
                   else 
             
             
                 
                     next application server 
             
             
                 
                   endif 
             
             
                 
                 endif 
             
             
                 
               endfor 
             
             
                 
                 
             
           
        
       
     
   
   In the above algorithm, the bypass condition is automatically set to fault unless some bypass condition is met, which sets the bypass condition to true. A bypass condition is any one of a number of conditions that may be used to cause the algorithm to refuse acceptance of the message. As an example, the bypass condition may be a message to start a new session, as explained above. In such a case, when a message to start a new session is received, the bypass condition becomes true and the message is thus refused, and not processed by the algorithm. 
   The description of the algorithm has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the algorithm to the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments described were chosen and described in order to best explain the principles of the implementation of the algorithm, the practical application, and to enable others of ordinary skill in the art to understand the algorithm for use in various embodiments with various modifications as are suited to the particular use contemplated. For example, the algorithm may be easily modified to encompass prioritizing the order in which to try the various application servers. All such subtle variations are contemplated and intended to be included in the scope of various exemplary embodiments. 
     FIG. 4  is a flowchart illustrating the operation of reducing session initiation protocol latency in a Java environment in accordance with an exemplary embodiment. The operation of  FIG. 4  may be implemented by an on demand router, such as on demand router  302  in  FIG. 3  and more specifically by a load balancer, such as load balancer  324  in  FIG. 3 . The operation begins when the load balancer receives statistics regarding garbage collection activities of a server (step  402 ). Next the operation analyzes the statistics (step  404 ), and optimizes the garbage collection activities based on the statistics (step  406 ), whereupon the operation ends. 
   Optimization of the garbage collection activities can be either proactive or reactive in nature. That is, garbage collection activities could be optimized based on the current statistics in order to handle the current garbage collection needs of the system. Alternatively, the statistics may be used to predict the future garbage collection needs of the system. The garbage collection activities may then be optimized to meet the predicted future garbage collection needs of the system. 
   The invention can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment containing both hardware and software elements. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, etc. 
   Furthermore, the invention can take the form of a computer program product accessible from a computer-usable or computer-readable medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable medium can be any tangible apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. 
   The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W) and DVD. 
   A data processing system suitable for storing and/or executing program code will include at least one processor coupled directly or indirectly to memory elements through a system bus. The memory elements can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution. 
   Input/output or I/O devices (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers. 
   Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters. 
   The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.