Maintaining System Memory Configuration Guide, Cisco IOS Release 15S
Memory Leak Detector
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Memory Leak Detector

Memory Leak Detector

The Memory Leak Detector feature is a tool that can be used to detect memory leaks on a router that is running Cisco IOS software. The Memory Leak Detector feature is capable of finding leaks in all memory pools, packet buffers, and chunks.

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information for Memory Leak Detector.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http:/​/​www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for Memory Leak Detector

  • You should have at least a basic familiarity with the Cisco IOS environment and the command-line interface.

  • You should have at least a minimal configuration running on your system.

Restrictions for Memory Leak Detector

  • You must have your network up and running, with Cisco IOS Release 12.2 or a later release installed.

  • Some of the Cisco IOS configuration commands are only available on certain router platforms, and the command syntax may vary on different platforms.

Information About Memory Leak Detector

Memory Leaks

Memory leaks are static or dynamic allocations of memory that do not serve any useful purpose. Although technology is available for detection of leaks among statically allocated memory, in this document the focus is on memory allocations that are made dynamically.

Memory Leak Detection

From the detection point of view, leaks among the dynamically allocated memory blocks can be classified into the following three types:

  • Type 1 leaks have no references. These blocks of memory can not be accessed.

  • Type 2 leaks are part of one or more cycles of allocations but none of the blocks in these cycles is accessible from outside of the cycles. Blocks within each cycle have references to other elements in the cycle(s). An example of a Type 2 leak is a circular list that is not needed anymore. Though individual elements are reachable, the circular list is not reachable.

  • Type 3 leaks are accessible or reachable but are not needed, for example, elements in data structures that are not needed anymore. A subclass of Type 3 leaks are those where allocations are made but never written to. You can look for these subclass leaks using the showmemorydebugreferenceunused command.

The Memory Leak Detector feature provides the technology to detect Type 1 and Type 2 memory leaks.

The Memory Leak Detector feature works in the following two modes:

  • Normal mode--Where memory leak detector uses memory to speed up its operations.

  • Low memory mode--Where memory leak detector runs without attempting to allocate memory.

Low memory mode is considerably slower than the normal mode and can handle only blocks. There is no support for chunks in low memory mode. Low memory mode is useful when there is little or no memory available on the router.

The memory leak detector has a simple interface and can be invoked by the command line interface (CLI) at any time to get a report of memory leaks. For testing purposes, you can perform all tests, then invoke memory leak detector to get a report on leaks. If you are interested only in leaks generated by your test cases alone, memory leak detector has an incremental option, which can be enabled at the start of testing. After testing completes, you can get a report on only the leaks that occurred after the incremental option was enabled.

To reduce false alarms, it is mandatory that memory leak detector be invoked multiple times and that only leaks that consistently appear in all reports be interpreted as leaks. This is especially true for packet buffer leaks.


Note


When submitting defects based on the reports of memory leak detector, please add “memleak-detection” to the attribute field of the defect report.


DANGER

Executing memory leak detection commands on a device with a serious memory leak issue may cause loss of connectivity.

How to Use Memory Leak Detector

Displaying Memory Leak Information

To display detected memory leak information, complete the task in this section:

SUMMARY STEPS

    1.    enable

    2.    show memory debug leaks [chunks | largest | lowmem | summary]


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 show memory debug leaks [chunks | largest | lowmem | summary]


    Example:
    Router# show memory debug leaks chunks
     

    Invokes normal mode memory leak detection and displays detected memory leaks. Optional keywords are as follows:

    • chunks --Invokes normal mode memory leak detection and displays detected memory leaks in chunks.

    • largest --Invokes memory leak detection and displays the top ten leaking allocator_pcs and total amount of memory that they have leaked. Additionally, each time this command is invoked it remembers the previous invocation's report and compares it to the current invocation's report.

    • lowmem --Invokes low memory mode memory leak detection and displays detected memory leaks. The amount of time taken for analysis is considerably greater than that of normal mode. The output for this command is similar to the showmemorydebugleaks command.

    • summary --Invokes normal mode memory leak detection and displays detected memory leaks based on allocator_pc and then on the size of the block.

     

    Setting the Memory Debug Incremental Starting Time

    To set the starting time for incremental analysis of memory leaks, complete the task in this section:

    SUMMARY STEPS

      1.    enable

      2.    set memory debug incremental starting-time


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 set memory debug incremental starting-time


      Example:
      Router# set memory debug incremental starting-time
       

      Sets the starting time for incremental analysis to the time when the command is issued. When the starting time is set, only memory allocated after the starting time will be considered for reporting as leaks.

       

      Displaying Memory Leak Information Incrementally

      To display memory leak information after a starting time has been established, complete the tasks in this section:

      SUMMARY STEPS

        1.    enable

        2.    set memory debug incremental starting-time

        3.    show memory debug incremental {allocations | leaks [lowmem] | status}


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2 set memory debug incremental starting-time


        Example:
        Router# set memory debug incremental starting-time
         

        Sets the starting time for incremental analysis to the time when the command is issued.

         
        Step 3 show memory debug incremental {allocations | leaks [lowmem] | status}


        Example:
        Router# show memory debug incremental allocations


        Example:
        
        
                
         
        • allocations --Displays all the memory blocks that were allocated after the issue of a setmemorydebugincrementalstarting-time command. The displayed memory blocks are just memory allocations, they are not necessarily leaks.

        • leaks --Displays output similar to the showmemorydebugleaks command, except that it displays only memory that was leaked after the issue of a setmemorydebugincrementalstarting-time command.

        • lowmem --Forces memory leak detection to work in low memory mode. The output for this command is similar to the showmemorydebugleaks command, except that it displays only memory that was leaked after the issue of a setmemorydebugincrementalstarting-time command.
          • In low memory mode, the analysis time is considerably greater than it is in normal mode.
          • You can use this command when you already know that normal mode memory leak detection will fail (perhaps by an unsuccessful previous attempt to invoke normal mode memory leak detection).
        • status --Displays whether a starting point for incremental analysis has been set and the elapsed time since then.

         

        Examples for Memory Leak Detector

        Example show memory debug leaks

        The following example shows output from the showmemorydebugleaks command with no optional keywords specified:

        Router# show memory debug leaks
        Adding blocks for GD...
                         PCI memory
        Address    Size   Alloc_pc  PID  Name
                         I/O memory
        Address    Size   Alloc_pc  PID  Name
                         Processor memory
        Address    Size   Alloc_pc  PID  Name
        62DABD28       80 60616750  -2   Init
        62DABD78       80 606167A0  -2   Init
        62DCF240       88 605B7E70  -2   Init
        62DCF298       96 605B7E98  -2   Init
        62DCF2F8       88 605B7EB4  -2   Init
        62DCF350       96 605B7EDC  -2   Init
        63336C28      104 60C67D74  -2   Init
        63370D58       96 60C656AC  -2   Init
        633710A0      304 60C656AC  -2   Init
        63B2BF68       96 60C659D4  -2   Init
        63BA3FE0    32832 608D2848  104  Audit Process
        63BB4020    32832 608D2FD8  104  Audit Process
        

        The table below describes the significant fields shown in the display.

        Table 1 show memory debug leaks Field Descriptions

        Field

        Description

        Address

        Hexadecimal address of the leaked block.

        Size

        Size of the leaked block (in bytes).

        Alloc_pc

        Address of the system call that allocated the block.

        PID

        The process identifier of the process that allocated the block.

        Name

        The name of the process that allocated the block.

        Example show memory debug leaks chunks

        The following example shows output from the showmemorydebugleakschunks command:

        Router# show memory debug leaks chunks
        Adding blocks for GD...
                         PCI memory
        Address    Size   Alloc_pc  PID  Name
        Chunk Elements:
        Address  Size  Parent   Name
                         I/O memory
        Address    Size   Alloc_pc  PID  Name
        Chunk Elements:
        Address  Size  Parent   Name
                         Processor memory
        Address    Size   Alloc_pc  PID  Name
        62DABD28       80 60616750  -2   Init
        62DABD78       80 606167A0  -2   Init
        62DCF240       88 605B7E70  -2   Init
        62DCF298       96 605B7E98  -2   Init
        62DCF2F8       88 605B7EB4  -2   Init
        62DCF350       96 605B7EDC  -2   Init
        63336C28      104 60C67D74  -2   Init
        63370D58       96 60C656AC  -2   Init
        633710A0      304 60C656AC  -2   Init
        63B2BF68       96 60C659D4  -2   Init
        63BA3FE0    32832 608D2848  104  Audit Process
        63BB4020    32832 608D2FD8  104  Audit Process
        Chunk Elements:
        Address  Size  Parent   Name
        62D80DA8    16 62D7BFD0 (Managed Chunk )
        62D80DB8    16 62D7BFD0 (Managed Chunk )
        62D80DC8    16 62D7BFD0 (Managed Chunk )
        62D80DD8    16 62D7BFD0 (Managed Chunk )
        62D80DE8    16 62D7BFD0 (Managed Chunk )
        62E8FD60   216 62E8F888 (IPC Message He)
        

        The table below describes the significant fields shown in the display.

        Table 2 show memory debug leaks chunks Field Descriptions

        Field

        Description

        Address

        Hexadecimal address of the leaked block.

        Size

        Size of the leaked block (in bytes).

        Alloc_pc

        Address of the system call that allocated the block.

        PID

        The process identifier of the process that allocated the block.

        Name

        The name of the process that allocated the block.

        Size

        (Chunk Elements) Size of the leaked element (bytes).

        Parent

        (Chunk Elements) Parent chunk of the leaked chunk.

        Name

        (Chunk Elements) The name of the leaked chunk.

        Example show memory debug leaks largest

        The following example shows output from the showmemorydebugleakslargest command:

        Router# show memory debug leaks largest
        Adding blocks for GD...
                         PCI memory
        Alloc_pc    total leak size
                         I/O memory
        Alloc_pc    total leak size
                         Processor memory
        Alloc_pc    total leak size
        608D2848    32776     inconclusive
        608D2FD8    32776     inconclusive
        60C656AC    288       inconclusive
        60C67D74    48        inconclusive
        605B7E98    40        inconclusive
        605B7EDC    40        inconclusive
        60C659D4    40        inconclusive
        605B7E70    32        inconclusive
        605B7EB4    32        inconclusive
        60616750    24        inconclusive
        

        The following example shows output from the second invocation of the showmemorydebugleakslargest command:

        Router# show memory debug leaks largest
        Adding blocks for GD...
                         PCI memory
        Alloc_pc    total leak size
                         I/O memory
        Alloc_pc    total leak size
                         Processor memory
        Alloc_pc    total leak size
        608D2848    32776
        608D2FD8    32776
        60C656AC    288
        60C67D74    48
        605B7E98    40
        605B7EDC    40
        60C659D4    40
        605B7E70    32
        605B7EB4    32
        60616750    24
        

        Example show memory debug leaks summary

        The following example shows output from the showmemorydebugleakssummary command:

        Router# show memory debug leaks summary
        Adding blocks for GD...
                         PCI memory
        Alloc PC        Size     Blocks      Bytes    What
                         I/O memory
        Alloc PC        Size     Blocks      Bytes    What
                         Processor memory
        Alloc PC        Size     Blocks      Bytes    What
        0x605B7E70 0000000032 0000000001 0000000032    Init
        0x605B7E98 0000000040 0000000001 0000000040    Init
        0x605B7EB4 0000000032 0000000001 0000000032    Init
        0x605B7EDC 0000000040 0000000001 0000000040    Init
        0x60616750 0000000024 0000000001 0000000024    Init
        0x606167A0 0000000024 0000000001 0000000024    Init
        0x608D2848 0000032776 0000000001 0000032776    Audit Process
        0x608D2FD8 0000032776 0000000001 0000032776    Audit Process
        0x60C656AC 0000000040 0000000001 0000000040    Init
        0x60C656AC 0000000248 0000000001 0000000248    Init
        0x60C659D4 0000000040 0000000001 0000000040    Init
        0x60C67D74 0000000048 0000000001 0000000048    Init
        

        The table below describes the significant fields shown in the display.

        Table 3 show memory debug leaks summary Field Descriptions

        Field

        Description

        Alloc PC

        Address of the system call that allocated the block.

        Size

        Size of the leaked block.

        Blocks

        Number of blocks leaked.

        Bytes

        Total amount of memory leaked.

        What

        Name of the process that owns the block.

        Example show memory debug incremental allocations

        The following example shows output from the showmemorydebugincremental command when entered with the allocations keyword:

        Router# show memory debug incremental allocations
        Address    Size   Alloc_pc  PID  Name
        62DA4E98      176 608CDC7C  44   CDP Protocol
        62DA4F48       88 608CCCC8  44   CDP Protocol
        62DA4FA0       88 606224A0  3    Exec
        62DA4FF8       96 606224A0  3    Exec
        635BF040       96 606224A0  3    Exec
        63905E50      200 606A4DA4  69   Process Events

        Example show memory debug incremental status

        The following example shows output from the showmemorydebugincremental command entered with the status keyword:

        Router# show memory debug incremental status
        Incremental debugging is enabled
        Time elapsed since start of incremental debugging: 00:00:10

        Additional References

        The following sections provide references related to Memory Leak Detector.

        Related Documents

        Related Topic

        Document Title

        Cisco IOS commands

        Cisco IOS Master Commands List, All Releases

        Cisco IOS configuration commands

        Cisco IOS Configuration Fundamentals Command Reference

        Standards

        Standards

        Title

        No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

        --

        MIBs

        MIBs

        MIBs Link

        No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

        To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

        http:/​/​www.cisco.com/​go/​mibs

        RFCs

        RFCs

        Title

        No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

        --

        Technical Assistance

        Description

        Link

        Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

        http:/​/​www.cisco.com/​public/​support/​tac/​home.shtml

        Feature Information for Memory Leak Detector

        The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

        Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

        Table 4 Feature Information for Memory Leak Detector

        Feature Name

        Releases

        Feature Information

        Memory Leak Detector

        12.3(8)T1 12.2(25)S

        The Memory Leak Detector feature is a tool that can be used to detect memory leaks on a router that is running Cisco IOS software. The Memory Leak Detector feature is capable of finding leaks in all memory pools, packet buffers, and chunks.

        Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)