Patent Publication Number: US-7900092-B2

Title: Kernel-level method of flagging problems in applications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/486,638 entitled KERNEL-LEVEL METHOD OF FLAGGING PROBLEMS IN APPLICATIONS filed on Jul. 11, 2003. 
    
    
     TECHNICAL FIELD 
     This application relates to flagging applications that may have memory leak and other resource usage problems using data collected at the kernel level. 
     BACKGROUND 
     Many currently available debugging tools require that programs be compiled and run in a different environment than their normal runtime environment, for example, with instrumented libraries and modules specifically used for debugging purposes. In addition, most debugging tools require many manual steps and time-consuming manual analysis in order to determine problems in an application. A hands-off tool that identifies potential problems with no intrusion to the applications while they are running in their natural run-time environment is desirable. 
     SUMMARY 
     A method of identifying potential problems in applications is provided. The method in one embodiment comprises monitoring at a kernel level system resource usage of one or more running applications without modifying run-time environments of the running applications and identifying from the monitored system usage, an application whose system usage pattern satisfies a predetermined criteria associated with one or more problems. The system resource usage may include, but is not limited to memory usage. 
     A system for identifying problems in applications in one embodiment comprises a data collection module and a data analysis module. The data collection module in one aspect is operable to retrieve information about a running application at a kernel level. The data analysis module in one aspect is operable to determine from the retrieved information one or more system usage patterns that may be associated with one or more problems. 
     Further features as well as the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a system kernel and various modules including the problem identifying module of the present disclosure in one embodiment. 
         FIG. 2  illustrates a flow diagram for monitoring kernel level system resource usage and collecting the related information. 
         FIG. 3  illustrates a flow diagram for analyzing the kernel level information. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a block diagram illustrating a system kernel and various modules including the problem identifying module of the present disclosure in one embodiment. The block diagram shown in  FIG. 1  is presented for illustrative purposes only. Other Unix systems may have kernel models that deviate from the one shown in  FIG. 1 . Further, the problem identifying module of the present disclosure is not limited to applications in Unix Systems only, but rather, may be applied to other systems such as Windows, NT, Linux.  FIG. 1  shows two levels: user  102  and kernel  104 . The system call interface  106  represents the border between user programs  108   a ,  108   b  and the kernel. Libraries  110  map system calls invoked by the user programs  108   a ,  108   b  to the primitives needed to enter the kernel level  104 . Assembly language programs may invoke system calls directly without a system call library. The libraries  110  are linked with the user programs  108   a ,  108   b  at compile time and thus may be considered as part of the user programs  108   a ,  108   b.    
     The kernel level shown in  FIG. 1  is partitioned into two subsystems: file subsystem  112  and process control subsystem  118 . The file subsystem  112  accesses file data, for example, using buffering mechanism  114  that regulates data flow between the operating system and secondary storage devices via device drivers  116 . The process control subsystem  118  is responsible for process synchronization  119 , interprocess communication  120 , memory management  122 , and process scheduling  124 . The file subsystem  112  and the process control subsystem  118  interact, for example, when loading a file into memory for execution. The process control subsystem  118  reads executable files into memory before executing them. The memory management module  124  controls the allocation of memory. The scheduler module  122  allocates the CPU (central processing unit) to processes. The system interprocess communications  120  include asynchronous signaling of events and synchronous transmission of messages between processes. The hardware control  126  is responsible for handling interrupts and for communicating with the machine. 
     A process is the execution of a program and comprises a pattern of bytes that the CPU interprets as machine instructions (text), data, and stack. Several processes  128   a ,  128   b  or  130   a ,  130   b  may be instances of a user program  108   a  or  108   b . The kernel loads an executable file into memory during, for example, an exec system call, and the loaded process comprises of at least three parts called regions: text, data, and the stack. A running process, thus, in one embodiment uses separate memory areas, allocating and deallocating the memory areas as the process runs. That is, once a process performs its desired functions, allocated memory is freed for other use. Similarly, a user program  108   a  or  108   b  may spawn one or more children processes and those children processes may in turn spawn additional processes to perform various tasks. Once the tasks are performed, however, under normal conditions, those processes should exit, either gracefully or with error conditions. 
     The data collection module  132  in one embodiment collects data related to the user programs  108   a ,  108   b  while allowing the user programs  108   a ,  108   b  to run in their natural run-time environment or mode, for example, without having to be recompiled or relinked to be run in a debug mode. The data collected by the data collection module  132 , for example, may include, but are not limited to, information about the memory such as the text, data, and stack memory used by the user programs  108   a ,  108   b , the number of running or created processes per user programs  108   a ,  108   b , the CPU usage per user programs  108   a ,  108   b , and any other kernel or system resource usage data related to the user programs  108   a ,  108   b.    
     The data collection module  132  in one embodiment utilizes exiting debugging tools to obtain the selected data. For example, the Q4 debugger released with Hewlett Packard&#39;s operating system, Linux kernel debuggers KDB or GDB, or the modular debugger (MDB) for Solaris may be utilized to retrieve information about the kernel space data and the various state of the system while the user programs  108   a ,  108   b  are running. An example of a Q4 script for retrieving such information may include calling Q4 as q4-p/stand/vmunix/dev/mem, then invoking a script (such as a Perl script) that drives per-process data collection and saves selected fields of the output in a human readable format. 
     Similarly, other debugging tools may be used to generate a script for programmatically retrieving various system information at a kernel level. The retrieved information may be stored, for example, as a log file  138 . 
     The data analysis module  134  may identify user programs that may have problems such as memory leaks, orphan processes by analyzing the information stored in the log file  138 . The analysis may involve filtering the information and selecting those that meet predetermined criteria as described in more detail with reference to  FIG. 3 . 
       FIG. 2  illustrates a flow diagram for monitoring kernel level system resource usage and collecting the related information. The monitoring and collecting, for example, may be performed periodically by executing existing kernel debugger facilities and extracting selected fields of data from the kernel debugger output. At  202 , an interval period for monitoring is obtained, for instance, from a command line, from a file, or as an input to a query, or any other method for receiving input information. The interval, for example, may be every 600 seconds or the like. In another embodiment, the interval period may be obtained using starting and end time for monitoring. For example, a user may specify begin and end time and a number of times to monitor during that period. 
     At  204 , processes that are running in a system are determined, for example, by calling subroutine LoadAllProcs. At  206 , system resource statistics is obtained for each process running. The system resource statistics may be obtained by using existing facilities such as the Q4, MDB, or any other appropriate kernel debugging utilities, e.g., gdb/boot/vmlinux/dev/mem. For example, using the Q4 utility, memory page count allocated and used by a running process may be obtained and logged. The memory page count may be further typed into different types of memory being used by the running process: for example, text, data, and stack types. At  208 , this information may be saved in a log file. The log file, for instance, may contain lines such as: 
     
       
         
           
               
               
               
               
               
             
               
                   
                   
               
               
                   
                 (PID) 
                 (TEXT) 
                 (DATA) 
                 (STACK) 
               
               
                   
                   
               
             
            
               
                   
                 0x001 
                 3 
                 5 
                 2 
               
               
                   
                 0x002 
                 5 
                 3 
                 6 
               
               
                   
                 . 
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                 . 
                 . 
               
               
                   
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                 . 
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                 . 
               
               
                   
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                 . 
                 . 
               
               
                   
                 0x003 
                 4 
                 9 
                 9 
               
               
                   
                 0x001 
                 2 
                 7 
                 2 
               
               
                   
                 0x003 
                 5 
                 11  
                 7 
               
               
                   
                   
               
            
           
         
       
     
     Similarly, a number of processes associated with a user program may be obtained to determine if any of the processes are defunct or orphaned by using respectively the process status or parent pid field as a selection criterion. 
     At  210 , the method waits for the amount of time equivalent to the interval period, for example, by a sleep call for that amount of time. At  212 , it is determined as to whether more monitoring is to be performed. If the monitoring is to continue, the method returns to  204 . Otherwise, the method stops, performing any cleanups such as releasing memory, closing files, and exiting any children processes gracefully. 
       FIG. 3  illustrates a flow diagram for analyzing the kernel level information. At  302 , the file that contains the system resource usage information is opened. At  304 , the information is read. A line of a file, for example, may contain a process identifier and the memory usage for that process as shown above. In another example, a line of a file may contain an application identifier and the number of processes that are spawned by the process. In yet another example, a line of a file may contain a process identifier and the CPU usage for that process. At  306 , the information is used to determine whether an abnormal pattern or condition exists. An abnormal pattern may exist, for example, if one particular process&#39;s memory size increases continuously from period to period; if one particular long-running process&#39;s memory size continually increases without any decrease in size during that number of interval periods; if a process is running even when a parent process is not (orphan process); if a process is continuously spawning new processes. 
     A continuous increase in memory size for a particular process, for example, may be detected if the memory size logged in the log file ( 138   FIG. 1 ) for that process has increased from one period to another period of monitoring. A comparison of a memory size from the previous period to the current period, for example, may determine whether there is an increase from one period to another period. A number of increases then may be stored in a buffer and compared with a predetermined number to determine if the increase is excessive. Picking the right query interval and duration of testing depends on the application and should be chosen appropriately (e.g., every 60 seconds). 
     An existence of orphan process is detected, for example, if no parent process for a particular process is found in the log file as one of the running processes. In another example, a process is detected as spawning unusually large number of children processes if a predetermined number of processes all have the same parent process identifiers. At  308 , the application or the process identifier detected as meeting the abnormal pattern or condition is then saved, for example, in another file ( 140   FIG. 1 ). At  310 , if there are more lines to read in the log file, the method continues to  304 . Otherwise, at  312 , the method stops. 
     The system and method of the present disclosure may be implemented and run on a general-purpose computer. The system and method of the present disclosure, for example, may be utilized during development of application programs or when run at a customer&#39;s site, for example, to detect and identify possible problems associated with the application programs. The embodiments described above are illustrative examples and it should not be construed that the present invention is limited to these particular embodiments. Although the description was provided using the Unix system as an example, it should be understood that the method and system disclosed in the present application may apply to any other computer operating systems. Thus, various changes and modifications may be effected by one skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.