Abstract:
A bottleneck detection system, a measurement object server, a bottleneck detection method and a program capable of specifying a factor that causes a bottleneck on the occasion of concurrent processing of a plurality of transactions. A tracer collects execution histories of a measurement object server processing transactions with a specified amount of load. An analyzer receives the execution histories from the tracer and analyzes them to measure performance indices with respect to software components in the measurement object server. A determination section receives the analysis results from the analyzer and, processes a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a bottleneck detection system, a measurement object server, a bottleneck detection method and a program for detecting a bottleneck on the occasion of concurrent processing of a plurality of transactions. 
   BACKGROUND OF THE INVENTION 
   In Takashi Horikawa, “Performance Analysis of a Client-Server System Using Queueing Networks: A Case Study,” Int. Trans. Opl Res. Vol. 4, No. 3, pp. 199-209, 1997, there is described an example of a technology to evaluate the performance of a system (hereinafter referred to as “server”) that concurrently processes a plurality of processing or computing requirements (hereinafter referred to as “transactions”). 
   According to the technology, an evaluation is made as to the performance of a server processing a plurality of transactions (mainly the relation between the throughput of the server and response times for transactions) by using performance basic data: the time spent on server resources (CPUs and disks) used to process a single transaction, and a performance evaluation model based on a queuing network theory. 
   Here, for example, as in a description shown in http://www.hyperformix.com/Default.asp?Page=210, a performance simulator may be used as the performance evaluation model. In this case, input data and output results of the performance evaluation are similar to those of the aforementioned technology. 
   With the performance evaluation model used in the technology, the performance is evaluated on the assumptions as follows: 
   1) The server resource time required to process a single transaction is unchanged even if there is a variation in the number of transactions to be processed by the server per unit of time 
   2) A plurality of transactions compete only for server resources corresponding to input data 
   Thus, for a server (including software that processes transactions) that satisfies those conditions, the result (the relation between the throughput of the server and response times for transactions) obtained by the performance evaluation model sufficiently reflects the actual server performance. 
   On the other hand, in the case of a server that does not satisfy the condition 1), the server has a bottleneck in the server resource whose utilization increases when processing a plurality of transactions. 
   Besides, in the case of a server that does not satisfy the condition 2), a factor that is not reflected in the performance evaluation model constitutes the bottleneck of the real server. Consequently, there occurs a problem (performance problem) that the performance thereof is lower than the result obtained by the performance evaluation model. 
     FIGS. 1 and 2  are diagrams showing conditions where a server having four CPUs (Central Processing Units) concurrently starts processing four transactions to illustrate concrete examples of the problem. 
     FIG. 1  shows the case where there is a process that requires exclusive control (that cannot be processed concurrently with other transactions) during transaction processing, and a busy wait is used by a CPU to obtain the execution permission. 
   In this case, it takes 3 units of CPU time to process a single transaction. In  FIG. 1 , however, the processing of transactions requires 3, 4, 5 and 6 units of CPU time, respectively. That is, on the average, the CPU time taken to process a single transaction increases to 4.5 units. 
     FIG. 2  shows the case where a process that requires exclusive control uses semaphores, etc. to obtain the execution permission without using a CPU. When not performing exclusive control, the server having four CPUs can process 4/3 transactions each requiring 3 units of CPU processing per unit of time. In  FIG. 2 , however, the semaphores used for exclusive control constitute a bottleneck, and the server can process only a single transaction per unit of time. Namely, the server performance is lower than the evaluation. 
   Additionally, in Japanese Patent Application laid open No. 2001-14189, for example, there has been proposed a technology to find a transaction processing process that constitutes a bottleneck in a transaction processing system. According to the technology, each transaction processing process is provided with an interface to send back CPU utilization time. The processing performance of each transaction processing process can be measured together with that of the entire transaction processing system, and the processing performances of the individual processes are measured at the same time. 
   The conventional technologies, however, have the following problems. 
   It is necessary to find and eliminate the bottleneck of a real server to solve the aforementioned performance problems so that the server performs as evaluated by the performance evaluation model. However, in the conventional technologies, there has been no standard method to find out the factor that causes the bottleneck and the cause (whether the bottleneck is caused as in the case of  FIG. 1  or  2 ). Consequently, an expert who has a special knowledge has to check the operation of a server using a combination of various measurement tools to evaluate the bottleneck based on the results and his/her experience. In other words, the bottleneck can be detected by only limited experts. Further, a considerable amount of time is required to find the bottleneck, and if the expert has missed the evaluation, countermeasures taken afterwards come to nothing. 
   That is, in an information processing system, especially, in a server that concurrently processes a plurality of transactions, even if there is no problem in the operation for processing a single transaction, a bottleneck occurs on the occasion of concurrent processing of a plurality of transactions. As a result, the system or server may not be able to perform as originally expected. To take countermeasures against the problem, it is necessary to specify the factor that causes the bottleneck in transaction processing software in question and the cause. However, there has been no systematic method to accomplish such purpose, and an expert has tried to find the cause by appropriately using various tools for monitoring the operating condition of a server. This requires a considerable amount of time and presents a substantial human resource problem, resulting in an increase in system configuration costs. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a bottleneck detection system, a measurement object server, a bottleneck detection method and software capable of specifying the factor that causes a bottleneck on the occasion of concurrent processing of a plurality of transactions. 
   In accordance with the first aspect of the present invention, to achieve the object mentioned above, there is provided a bottleneck detection system comprising a tracer for collecting execution histories of a measurement object server processing transactions with a specified amount of load, an analyzer for receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section for receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the second aspect of the present invention, there is provided a bottleneck detection system comprising a load generator for sending transactions to a measurement object server according to a specified amount of load, a tracer for collecting execution histories of the measurement object server processing the transactions, an analyzer for receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section for receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the third aspect of the present invention, there is provided a bottleneck detection system comprising a measurement object server for processing transactions, a load generator for sending transactions to the measurement object server according to a specified amount of load, a tracer for collecting execution histories of the measurement object server processing the transactions, an analyzer for receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section for receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the fourth aspect of the present invention, the bottleneck detection system in one of the first to third aspects further comprises a tabulator for receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, creating an analysis result table that indicates the relation between the amount of load and each of the performance indices, wherein the determination section processes values stored in the analysis result table by prescribed algorithms to detect a bottleneck. 
   In accordance with the fifth aspect of the present invention, in the bottleneck detection system in one of the first to fourth aspects, the determination section processes values by prescribed algorithms to detect a bottleneck factor and the cause. 
   In accordance with the sixth aspect of the present invention, in the bottleneck detection system in one of the first to fifth aspects, the amount of load is specified by a controller. 
   In accordance with the seventh aspect of the present invention, in the bottleneck detection system in one of the first to sixth aspects, the value that indicates the amount of load is obtained from a controller. 
   In accordance with the eighth aspect of the present invention, in the bottleneck detection system in one of the first to seventh aspects, the tracer collects at least two execution histories of the measurement object server when the server is overloaded (highly loaded) and underloaded (lowly loaded), and the determination section compares the resource utilization times and the elapsed times as the performance indices of the overloaded and underloaded server to detect a bottleneck. 
   In accordance with the ninth aspect of the present invention, in the bottleneck detection system in one of the first to eighth aspects, the measurement object server includes kernel probes installed in the OS (Operating System) kernel and application probes installed in the transaction processing software. The tracer collects at least two execution histories of the measurement object server when the server is overloaded and underloaded from the kernel probes and the application probes. The analyzer obtains the resource utilization time and the elapsed time as the performance indices with respect to each of the software components separated by the application probes. Based on the performance indices, the determination section specifies as a bottleneck the performance index of a software component indicating a larger time prolongation or delay as load increases compared to those of other software components. 
   In accordance with the tenth aspect of the present invention, in the bottleneck detection system in one of the first to ninth aspects, the prescribed algorithms obtain the wall-to-CPU time ratio [i]=elapsed or wall time [i]/CPU time [i] and the CPU time ratio [i]=CPU time [i]/CPU time [1] with respect to each software component in the analysis result table, and then obtain the average of the wall-to-CPU time ratios [i] and that of the CPU time ratios [i] of all the software components. The determination section compares the wall-to-CPU time ratio and the CPU time ratio of each software component with the respective average values to find a factor or a software component with a value that becomes substantially larger than the average value as load increases. The determination section recognizes as a bottleneck the CPU time of a software component with the CPU time ratio that becomes substantially larger than the average value. On the other hand, when the wall-to-CPU time ratio of a software component becomes substantially larger than the average value, the determination section determines that a factor other than the CPU time of the software component is a bottleneck. 
   In accordance with the eleventh aspect of the present invention, there is provided a measurement object server for processing transactions sent from a load generator according to a specified amount of load, the bottleneck of which is detected by the steps of a tracer collecting execution histories of the measurement object server processing the transactions, an analyzer receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm. 
   In accordance with the twelfth aspect of the present invention, in the measurement object server in the eleventh aspects, the bottleneck detection steps further include the steps of a tabulator receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, creating an analysis result table that indicates the relation between the amount of load and each of the performance indices, and the determination section processing values stored in the analysis result table by prescribed algorithms. 
   In accordance with the thirteenth aspect of the present invention, in the measurement object server in the eleventh or twelfth aspect, the bottleneck factor and the cause are specified by the determination section processing values by prescribed algorithms. 
   In accordance with the fourteenth aspect of the present invention, in the measurement object server in one of the eleventh to thirteenth aspects, the amount of load is specified by a controller. 
   In accordance with the fifteenth aspect of the present invention, in the measurement object server in one of the eleventh to fourteenth aspects, the value that indicates the amount of load is obtained from a controller. 
   In accordance with the sixteenth aspect of the present invention, in the measurement object server in one of the eleventh to fifteenth aspects, the tracer collects at least two execution histories of the measurement object server when the server is overloaded and underloaded, and the determination section compares the resource utilization times and the elapsed times as the performance indices of the overloaded and underloaded server. 
   In accordance with the seventeenth aspect of the present invention, the measurement object server in one of the eleventh to sixteenth aspects includes kernel probes installed in the OS kernel and application probes installed in the transaction processing software. The tracer collects at least two execution histories of the measurement object server when the server is overloaded and underloaded from the kernel probes and the application probes. The analyzer obtains the resource utilization time and the elapsed time as the performance indices with respect to each of the software components separated by the application probes. Based on the performance indices, the determination section specifies as a bottleneck the performance index of a software component indicating a larger time prolongation as load increases compared to that of other software components. 
   In accordance with the eighteenth aspect of the present invention, in the measurement object server in one of the eleventh to seventeenth aspects, the prescribed algorithms obtain the wall-to-CPU time ratio [i]=wall time [i]/CPU time [i] and the CPU time ratio [i]=CPU time [i]/CPU time [1] with respect to each software component in the analysis result table, and then obtain the average of the wall-to-CPU time ratios [i] and that of the CPU time ratios [i] of all the software components. The wall-to-CPU time ratio and the CPU time ratio of each software component are compared to the respective average values to find a software component with a value that becomes substantially larger than the average value as load increases. The CPU time of a software component with the CPU time ratio that becomes substantially larger than the average value is regarded as the bottleneck. On the other hand, when the wall-to-CPU time ratio of a software component becomes substantially larger than the average value, a factor other than the CPU time of the software component is regarded as a bottleneck. 
   In accordance with the nineteenth aspect of the present invention, there is provided a bottleneck detection method comprising the steps of a tracer collecting execution histories of a measurement object server processing transactions with a specified amount of load, an analyzer receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the twentieth aspect of the present invention, there is provided a bottleneck detection method comprising the steps of a load generator sending transactions to a measurement object server according to a specified amount of load, a tracer collecting execution histories of the measurement object server processing the transactions, an analyzer receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the twenty-first aspect of the present invention, there is provided a bottleneck detection method comprising the steps of a load generator sending transactions to a measurement object server according to a specified amount of load, the measurement object server processing the transactions, a tracer collecting execution histories of the measurement object server processing the transactions, an analyzer receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the twenty-second aspect of the present invention, the bottleneck detection method in one of the nineteenth to twenty-first aspects further comprises the step of a tabulator receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, creating an analysis result table that indicates the relation between the amount of load and each of the performance indices, wherein the determination section processes values stored in the analysis result table by prescribed algorithms to detect a bottleneck. 
   In accordance with the twenty-third aspect of the present invention, in the bottleneck detection method in one of the nineteenth to twenty-second aspects, the determination section processes values by prescribed algorithms to detect a bottleneck factor and the cause. 
   In accordance with the twenty-fourth aspect of the present invention, in the bottleneck detection method in one of the nineteenth to twenty-third aspects, the amount of load is specified by a controller. 
   In accordance with the twenty-fifth aspect of the present invention, in the bottleneck detection method in one of the nineteenth to twenty-fourth aspects, the value that indicates the amount of load is obtained from a controller. 
   In accordance with the twenty-sixth aspect of the present invention, in the bottleneck detection method in one of the nineteenth to twenty-fifth aspects, the tracer collects at least two execution histories of the measurement object server when the server is overloaded and underloaded, and the determination section compares the resource utilization times and the elapsed times as the performance indices of the overloaded and underloaded server to detect a bottleneck. 
   In accordance with the twenty-seventh aspect of the present invention, in the bottleneck detection method in one of the nineteenth to twenty-sixth aspects, the measurement object server includes kernel probes installed in the OS kernel and application probes installed in the transaction processing software. The tracer collects at least two execution histories of the measurement object server when the server is overloaded and underloaded from the kernel probes and the application probes. The analyzer obtains the resource utilization time and the elapsed time as the performance indices with respect to each of the software components separated by the application probes. Based on the performance indices, the determination section specifies as a bottleneck the performance index of a software component indicating a larger time prolongation as load increases compared to that of other software components. 
   In accordance with the twenty-eighth aspect of the present invention, in the bottleneck detection method in one of the nineteenth to twenty-seventh aspects, the prescribed algorithms obtain the wall-to-CPU time ratio [i]=wall time [i]/CPU time [i] and the CPU time ratio [i]=CPU time [i]/CPU time [1] with respect to each software component in the analysis result table, and then obtain the average of the wall-to-CPU time ratios [i] and that of the CPU time ratios [i] of all the software components. The determination section compares the wall-to-CPU time ratio and the CPU time ratio of each software component with the respective average values to find a software component with a value that becomes substantially larger than the average value as load increases. The determination section recognizes as a bottleneck the CPU time of a software component with the CPU time ratio that becomes substantially larger than the average value. On the other hand, when the wall-to-CPU time ratio of a software component becomes substantially larger than the average value, the determination section determines that a factor other than the CPU time of the software component is a bottleneck. 
   In accordance with the twenty-ninth aspect of the present invention, there is provided software implementing a bottleneck detection method comprising the steps of a tracer collecting execution histories of a measurement object server processing transactions with a specified amount of load, an analyzer receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the thirtieth aspect of the present invention, there is provided software implementing a bottleneck detection method comprising the steps of a load generator sending transactions to a measurement object server according to a specified amount of load, a tracer collecting execution histories of the measurement object server processing the transactions, an analyzer receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the thirty-first aspect of the present invention, there is provided software implementing a bottleneck detection method comprising the steps of a load generator sending transactions to a measurement object server according to a specified amount of load, the measurement object server processing the transactions, a tracer collecting execution histories of the measurement object server processing the transactions, an analyzer receiving the execution histories from the tracer and analyzing them to measure performance indices with respect to software components in the measurement object server, and a determination section receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, processing a value that indicates the relation between the amount of load and each of the performance indices by a prescribed algorithm to detect a bottleneck. 
   In accordance with the thirty-second aspect of the present invention, the software in one of the twenty-ninth to thirty-first aspects further implements the step of a tabulator receiving the analysis results from the analyzer and, based on an obtained value that indicates the amount of load, creating an analysis result table that indicates the relation between the amount of load and each of the performance indices, wherein the determination section processes values stored in the analysis result table by prescribed algorithms to detect a bottleneck. 
   In accordance with the thirty-third aspect of the present invention, in the software in one of the twenty-ninth to thirty-second aspects, the determination section processes values by prescribed algorithms to detect a bottleneck factor and the cause. 
   In accordance with the thirty-fourth aspect of the present invention, in the software in one of the twenty-ninth to thirty-third aspects, the amount of load is specified by a controller. 
   In accordance with the thirty-fifth aspect of the present invention, in the software in one of the twenty-ninth to thirty-fourth aspects, the value that indicates the amount of load is obtained from a controller. 
   In accordance with the thirty-sixth aspect of the present invention, in the software in one of the twenty-ninth to thirty-fifth aspects, the tracer collects at least two execution histories of the measurement object server when the server is overloaded and underloaded, and the determination section compares the resource utilization times and the elapsed times as the performance indices of the overloaded and underloaded server to detect a bottleneck. 
   In accordance with the thirty-seventh aspect of the present invention, in the software in one of the twenty-ninth to thirty-sixth aspects, the measurement object server includes kernel probes installed in the OS kernel and application probes installed in the transaction processing software. The tracer collects at least two execution histories of the measurement object server when the server is overloaded and underloaded from the kernel probes and the application probes. The analyzer obtains the resource utilization time and the elapsed time as the performance indices with respect to each of the software components separated by the application probes. Based on the performance indices, the determination section specifies as a bottleneck the performance index of a software component indicating a larger time prolongation as load increases compared to that of other software components. 
   In accordance with the thirty-eighth aspect of the present invention, in the software in one of the twenty-ninth to thirty-seventh aspects, the prescribed algorithms obtain the wall-to-CPU time ratio [i]=wall time [i]/CPU time [i] and the CPU time ratio [i]=CPU time [i]/CPU time [1] with respect to each software component in the analysis result table, and then obtain the average of the wall-to-CPU time ratios [i] and that of the CPU time ratios [i] of all the software components. The determination section compares the wall-to-CPU time ratio and the CPU time ratio of each software component with the respective average values to find a software component with a value that becomes substantially larger than the average value as load increases. The determination section recognizes as a bottleneck the CPU time of a software component with the CPU time ratio that becomes substantially larger than the average value. On the other hand, when the wall-to-CPU time ratio of a software component becomes substantially larger than the average value, the determination section determines that a factor other than the CPU time of the software component is a bottleneck. 
   As is described above, in the bottleneck detection system, the measurement object server, the bottleneck detection method and the software in accordance with the present invention, an event trace is obtained by a combination of kernel probes and application probes. The event trace is analyzed to obtain performance indices with respect to each software component to thereby find a bottleneck. Thus, it is possible to specify a software component that causes the bottleneck when the load or transactions processed by the measurement object server increase. In addition, by the analysis of the event trace, the CPU utilization time and the elapsed time are obtained as the performance indices of each software component to find a bottleneck. Thus, it is possible to determine whether the CPU utilization time or another factor causes the bottleneck. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The exemplary aspects and features of the present invention will become more apparent from the consideration of the following detailed description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a diagram showing a condition where a conventional server having four CPUs concurrently starts processing four transactions; 
       FIG. 2  is a diagram showing another condition where a conventional server having four CPUs concurrently starts processing four transactions; 
       FIG. 3  is a schematic diagram showing a bottleneck detection system according to an embodiment of the present invention; 
       FIG. 4  is a diagram showing the representation and meaning of each event detected by kernel probes; 
       FIG. 5  is a diagram showing the representation and meaning of each event detected by application probes; 
       FIG. 6  is a sequence diagram showing the operation of respective software components of a measurement object server for processing a single transaction; 
       FIG. 7  is a sequence diagram showing the operation of the measurement object server for concurrently processing a plurality of transactions; 
       FIG. 8  is a sequence diagram showing operation for processing a single transaction during the concurrent processing of a plurality of transactions; 
       FIG. 9  is a diagram showing an example of a measurement condition table; 
       FIG. 10  is a flowchart showing the operation of a controller receiving the measurement condition table as input for sequentially sending instructions to other sections; 
       FIG. 11  is a diagram showing an example of an analysis result table; and 
       FIG. 12  is a diagram showing an example of the results of calculations based on the analysis result table. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, a description of a preferred embodiment of the present invention will be given in detail. 
     FIG. 3  is a schematic diagram showing a bottleneck detection system according to an embodiment of the present invention. Referring to  FIG. 3 , the bottleneck detection system comprises a measurement object server  10  that operates by software control, a load generator  11 , an analyzer  12 , a tabulator  13 , a determination section  14 , and a controller  15 . 
   The measurement object server  10  includes software components  1  to  3 , an OS (Operating System) kernel  4  and a tracer  5 . The OS kernel  4  has built-in kernel probes, while the software components  1  to  3  each have built-in application probes. 
   The load generator  11  sends transactions to the measurement object server  10  according to the amount of load specified by the controller  15 . 
   The measurement object server  10  receives the transactions sent from the load generator  11  through the OS kernel  4 . The OS kernel  4  passes the transactions to the software components  1  to  3  to process them. Thereby, the measurement object server  10  sends the processing results back to the source of the transaction request. 
   Besides, the tracer  5  receives information concerning software execution status from the kernel probes embedded in the OS kernel  4  and the application probes to record it as time series data (trace data). The tracer  5  initiates and terminates the trace data collection according to instructions from the controller  15 . 
   The analyzer  12  receives the trace data from the tracer  5  in the measurement object server  10  to analyze them according to instructions from the controller  15 . 
   The tabulator  13  receives the analysis results from the analyzer  12  and a value indicating the amount of load from the controller  15  to record them according to instructions from the controller  15 . 
   The controller  15  specifies the amount of load to instruct the load generator  11  to generate the load. The controller  15  also instructs the tracer  5  to initiate and terminate trace data collection. In addition, the controller  15  instructs the analyzer  12  to analyze the trace, and feeds the tabulator  13  with a value indicating the amount of the load to instruct it to perform tabulation. The controller  15  repeatedly performs a series of the operations while changing the amount of load so that the analysis results corresponding to respective amounts of load are stored in the tabulator  13  as an analysis result table. 
   The determination section  14  receives the analysis result table as input to find the bottleneck of the measurement object server  10  according to instructions from the controller  15 . 
   Referring next to  FIGS. 3 to 9 , a description will be given in detail of processing operation to detect a bottleneck according to the embodiment of the present invention. 
   First, transaction processing by the measurement object server  10  will be described. 
   In the measurement object server  10 , the OS kernel  4  and the software components  1  to  3  are involved in transaction processing. The OS kernel  4  is an operating system that supports the concurrent execution of a plurality of software processes (multiprocess). In the OS kernel  4 , kernel probes are placed at the parts to return or resume a process (start/restart CPU utilization) and to save a process (suspend/terminate CPU utilization), respectively. 
   The software components  1  to  3  configure software that processes transactions, and operate in order of the components  1 ,  2  and  3  to process transactions. In each of the software components  1  to  3 , application probes are placed at the start and end points of a transaction processed by the component, respectively. 
     FIG. 4  is a diagram showing the representation and meaning of each event detected by the kernel probes.  FIG. 5  is a diagram showing the representation and meaning of each event detected by the application probes. These representations are used in the following diagrams. 
     FIG. 6  is a sequence diagram showing the operation of the respective software components (the OS kernel  4  and the software components  1  to  3 ) of the measurement object server  10  for processing a single transaction. 
   On receipt of a transaction from the outside of the measurement object server  10 , the OS kernel  4  creates a process (n in  FIG. 6 ) for transaction processing and executes the process (event PRn). 
   Next, the process is transferred from the OS kernel  4  to the software component  1 , and the component  1  starts the transaction processing thereof (event AP 1   i ). Subsequently, the software component  1  requests the software component  2  to process the transaction. 
   Accordingly, the process is transferred from the software component  1  to the software component  2 , and the component  2  starts the transaction processing thereof (event AP 2   i ). Thereafter, the software component  2  requests the software component  3  to process the transaction. 
   Thereby, the process is transferred from the software component  2  to the software component  3 , and the component  3  starts the transaction processing thereof (event AP 3   i ). 
   On completion of the transaction processing, the software component  3  returns the processing result to the software component  2 , and terminates the process (event AP 3   o ). 
   The software component  2  processes the processing result received from the software component  3 . The software component  2  returns the processing result to the software component  1 , and terminates the process (event AP 2   o ). 
   The software component  1  processes the processing result received from the software component  2 . The software component  1  returns the processing result to the OS kernel  4 , and terminates the process (event AP 1   o ). 
   The OS kernel  4  returns the processing result received from the software component  1  to the source of the transaction request, and completes the execution of the process (n) in charge of the transaction processing (event PSn). 
   As is described above, one process is created for the processing of a single transaction. The process has a one-to-one correspondence with the transaction to complete the execution of the process on completion of the processing. 
     FIG. 7  is a sequence diagram showing an example of the operation of the measurement object server  10  for concurrently processing a plurality of transactions. For simplicity,  FIG. 7  shows events from the kernel probes only. 
   Referring to  FIG. 7 , in the condition where process  1  is operating, the execution of the process  1  is suspended (PS 1 ) and the execution of process  2  is started (PR 2 ) at time T 1 . 
   At time T 2 , the execution of the process  2  is suspended (PS 2 ) and the execution of process  4  is started (PR 4 ). 
   At time T 3 , the execution of the process  4  is suspended (PS 4 ) and the execution of the process  1  is restarted (PR 1 ). 
   At time T 4 , the execution of the process  1  is suspended (PS 1 ) and the execution of process  3  is started (PR 3 ). 
   At time T 5 , the execution of the process  3  is suspended (PS 3 ) and the execution of the process  2  is restarted (PR 2 ). 
   Such switching of processes is generally performed in the OS that supports multiprocess and performed at the time of autonomous or voluntary CPU utilization suspension or completion by a process or time slice (interrupts that occur at regular intervals). 
     FIG. 8  is a sequence diagram showing operation for processing a single transaction during the concurrent processing of a plurality of transactions. In  FIG. 8 , the process in charge of transaction processing is denoted by n as in  FIG. 6 . The operation of  FIG. 8  differs from that of  FIG. 6  in that process switching occurs while a CPU is used for transaction processing. In  FIG. 8 , the process save (event PSn) occurs at time T 3  and T 7 , and the process return or resume (event PRn) occurs at time T 4  and T 8 . 
   In the following, a description will be given of the tracer  5  and the analysis of an event trace obtained by the tracer  5 . 
   The tracer  5  has the function of recording all events that occur in the measurement object server  10  during a trace collection period as time series data. 
   An event to be traced herein corresponds to the kernel probes and application probes. That is, when these probes are executed with the execution of software in the measurement object server  10 , control is once transferred to the tracer  5 . The meaning or content of an event detected by the probes (see  FIGS. 4 and 5 ) and the occurrence time (approximate to the time at which the tracer  5  records the event) are stored as data on one event in a storage provided in the measurement object server  10 . After that, the execution of the software is restarted. 
   The occurrence time of an event may be obtained, for example, with a function offered by the CPU of the measurement object server  10 , or may be obtained by other known techniques. As the storage to store trace data may be used an area allocated to trace data in the main storage of the measurement object server  10 , or may be used an external storage medium. 
   The analyzer  12  analyzes trace data collected by the tracer  5  to obtain the CPU time (CPU utilization time) and elapsed time (wall or wall clock time) required for each transaction with respect to each software component. Incidentally, the CPU is given only as an example of a resource. Resources include disk, a network, a memory and the like. 
   A concrete calculation method will be described taking the event sequence or series of  FIG. 8  as an example. Referring to  FIG. 8 , the software component  1  starts the execution of process (AP 1   i ) at time T 2 , and transfers the process to the software component  2  at time T 5 . During the period, the software component  1  suspends the execution of the process (PSn) at time T 3 , and restarts it at time T 4  (hereinafter referred to as first half processing). 
   In addition, the software component  1  receives the processing result from the software component  2  at time T 10 , and processes it until time T 11 . Subsequently, the software component  1  passes the processing result to the OS kernel  4  as well as transferring the process thereto (hereinafter referred to as second half processing). 
   In this case, the elapsed time which it takes the software component  1  to perform the first half processing is T 5 −T 2 , and that to perform the second half processing is T 11 −T 10 . Thus, the entire elapsed time is (T 5 −T 2 )+(T 11 −T 10 ). 
   On the other hand, as to the CPU time for the first half processing, the CPU is not used during a period from time T 3  to T 4 . Therefore, the CPU time can be obtained by subtracting the period from the elapsed time, i.e., (T 5 −T 2 )−(T 4 −T 3 ). 
   Since the CPU utilization is not suspended during the second half processing, the CPU time for the second half processing is the same as the elapsed time (T 11 −T 10 ). Thus, the entire CPU time is (T 5 −T 2 )−(T 4 −T 3 )+(T 11 −T 10 ). 
   The elapsed time and CPU time can be calculated for the software components  2  and  3  in the same manner as above. Both the elapsed time and CPU time of the software component  2  are (T 6 −T 5 )+(T 10 −T 9 ). The elapsed time and CPU time of the software component  3  are (T 9 −T 6 ) and (T 9 −T 6 )−(T 8 −T 7 ), respectively. 
   As is described above, the elapsed time can be obtained by accumulating periods from when the software component starts its processing to when it transfers the process to another software component based on event time information detected by the application probes. Besides, the CPU time can be obtained by subtracting from the elapsed time a period during which CPU processing is suspended or accumulated periods from a process save event to a process return or resume event detected by the kernel probes. 
   On the basis of the above understanding, a description will be given of the method of detecting a bottleneck on the occasion of concurrent processing of a plurality of transactions. 
     FIG. 9  is a diagram showing an example of a measurement condition table.  FIG. 10  is a flowchart showing the operation of the controller  15  receiving the measurement condition table (shown in  FIG. 9 ) as input for sequentially sending instructions to other sections. 
   Each line in the measurement condition table corresponds to one measurement/analysis operation. In  FIG. 9 , the measurement/analysis operation is performed with respect to five degrees of load (1 transaction per second, 5 transactions per second, 10 transactions per second, 50 transactions per second, and 100 transactions per second). 
   The controller  15  first performs the measurement/analysis operation on the condition indicated in the first line. More specifically, the controller  15  indicates the amount of load (in this case, 1 transaction per second) listed in the first line of the measurement condition table to the load generator  11  to instruct it to generate the load. Then, the controller  15  waits a period of ramp-up time (a period of time until the measurement object server  10  becomes ready to steadily process the specified amount of load; in this case, 10 seconds) indicated in the first line of the measurement condition table (step S 1 ). On receipt of the load generation instruction, the load generator  11  sends transactions to the measurement object server  10  with specified frequency, and receives the processing results therefrom. 
   Next, the controller  15  instructs the tracer  5  to initiate the collection of trace data, and waits a period of measurement time (a period of time taken to collect the trace data; in this case, 100 seconds) indicated in the first line of the measurement condition table (step S 2 ). 
   Thereafter, the controller  15  instructs the tracer  5  to terminate the collection of trace data (step S 3 ). Thereby, the tracer  5  stores the trace data on the record of the operation (software execution history) of the measurement object server  10  during the period from the initiation to termination of the trace collection (measurement time) as previously described for the operation of the tracer  5 . 
   Subsequently, the controller  15  instructs the load generator  11  to terminate the generation of load, and waits a period of ramp-down time (a period of time until the measurement object server  10  returns to idle state after completing the transaction processing processed at that time; in this case, 15 seconds) indicated in the first line of the measurement condition table (step S 4 ). 
   After that, the controller  15  instructs the analyzer  12  to perform trace analysis, and waits for the completion of the analysis (step  5 ). 
   On receipt of the instruction, the analyzer  12  receives the trace data from the tracer  5  to analyze it according to algorithms set therein. Thereby, the analyzer  12  obtains the CPU time and elapsed time with respect to each software component. The analyzer  12  divides each of the values by the number of the transactions processed by the measurement object server  10  during the trace data collection period (in this embodiment, the number of the transactions corresponds to the number of processes for transaction processing performed by the measurement object server  10  during the trace data collection period) to obtain the average value per transaction. 
   The controller  15  indicates the amount of load (in this case, 1 transaction per second) in the measurement/analysis operation to the tabulator  13  to instruct it to tabulate the analysis results. 
   Having received the instruction, the tabulator  13  receives the analysis results (the average values of the CPU time and elapsed time per transaction with respect to each software component), and stores them in the analysis result table together with the specified amount of load. 
     FIG. 11  is a diagram showing an example of the analysis result table. Through the operation described above, the first line (the line in which the amount of load indicates 1 transaction per second) of the analysis result table is created. 
   By performing a series of the measurement/analysis operation, i.e., the process from step  1  through step  6 , on the condition indicated in each line of the measurement condition table shown in  FIG. 9  under the control of the controller  15  (corresponding to the loop of  FIG. 10 ), the entire analysis result table of  FIG. 11  can be created. 
   When the analysis result table of  FIG. 11  has been created, the controller  15  instructs the determination section  14  to find a bottleneck (step S 7 ). 
   On receipt of the instruction, the determination section  14  receives the analysis result table from the tabulator  13 , and processes it by preset algorithms to find a bottleneck factor and the cause. 
   The following are the algorithms set in the determination section  14  according to the embodiment of the present invention. First, the determination section  14  obtains the elapsed time-to-CPU time ratio (wall-to-CPU time ratio) [i]=elapsed time [i]/CPU time [i] and the CPU time ratio [i]=CPU time [i]/CPU time [1] with respect to each software component in the analysis result table. Then, the determination section  14  obtains the average of the elapsed time-to-CPU time ratios [i] and that of the CPU time ratios [i] of all the software components. Incidentally, [i] as used herein indicates the index of a value in the i-th line of the column corresponding to each item. 
     FIG. 12  is a diagram showing an example of the results of calculations based on the analysis result table. 
   The determination section  14  compares the elapsed time-to-CPU time ratio and the CPU time ratio with the respective average values with respect to each software component. Thereby, the determination section  14  finds a factor whose value becomes substantially larger (e.g., twice or more than twice the average value) than the average value as load increases. 
   In  FIG. 12 , the CPU time ratio of the software component  2  becomes substantially larger than the average value. Thus, the determination section  14  determines the CPU time of the software component  2  as a bottleneck. 
   Besides, if the determination section  14  finds that the elapsed time-to-CPU time ratio of a software component becomes substantially larger than the average value as a result of the calculations, it determines that a factor other than the CPU time of the software component is a bottleneck. 
   As set forth hereinabove, in accordance with the embodiment of the present invention, it is possible to specify a software component that causes a bottleneck when the load or the number of transactions processed by the measurement object server  10  increases. In addition, a determination can be made as to whether the CPU time or another factor causes the bottleneck. 
   While one preferred embodiment of the present invention has been shown, it is not so limited but is susceptible of various changes and modifications without departing from the scope and spirit of the present invention. For example, a program implementing the functions of the measurement object server  10  and respective sections may be loaded into a computer and executed to perform the functions of the bottleneck detection system. The program may be loaded into the computer from a computer-readable storage medium such as a CD-ROM (Compact Disc Read Only Memory) and a magnetic optical disk, or downloaded to the computer via a transmission medium such as the Internet and a telephone line. 
   In the embodiment described above, the bottleneck detection system has a construction in which the measurement object server  10  and individual sections are connected to each other. However, the respective functions may be implemented by a single computer system. Or a plurality of servers or the like may be added to the construction for the respective functions. The bottleneck detection system may comprise the measurement object server  10  having a construction to distribute processing load caused by load generation, a load generation device implementing the load generator  11 , and other devices for performing the functions of the respective sections. 
   While the present invention has been described with reference to the particular illustrative embodiment, it is not to be restricted by the embodiment but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention.