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Memory Leak Detector

Table Of Contents

Memory Leak Detector

Contents

Prerequisites for Memory Leak Detector

Restrictions for Memory Leak Detector

Information About Memory Leak Detector

Memory Leaks

Memory Leak Detection

How to Use Memory Leak Detector

Displaying Memory Leak Information

Setting the Memory Debug Incremental Starting Time

Displaying Memory Leak Information Incrementally

Examples for Memory Leak Detector

Example: show memory debug leaks

Example: show memory debug leaks chunks

Example: show memory debug leaks largest

Example: show memory debug leaks summary

Example: show memory debug incremental allocations

Example: show memory debug incremental status

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for Memory Leak Detector


Memory Leak Detector


Last Updated: December 3, 2010

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" section.

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.

Contents

Prerequisites for Memory Leak Detector

Restrictions for Memory Leak Detector

Information About Memory Leak Detector

How to Use Memory Leak Detector

Examples for Memory Leak Detector

Additional References

Feature Information for Memory Leak Detector

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 Leak Detection

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 show memory debug reference unused 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.



Warning 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

This section contains the following procedures:

Displaying Memory Leak Information

Setting the Memory Debug Incremental Starting Time

Displaying Memory Leak Information Incrementally

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 Action
Purpose

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 show memory debug leaks 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 Action
Purpose

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 Action
Purpose

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

allocations—Displays all the memory blocks that were allocated after the issue of a set memory debug incremental starting-time command. The displayed memory blocks are just memory allocations, they are not necessarily leaks.

leaks—Displays output similar to the show memory debug leaks command, except that it displays only memory that was leaked after the issue of a set memory debug incremental starting-time command.

lowmem—Forces memory leak detection to work in low memory mode. The output for this command is similar to the show memory debug leaks command, except that it displays only memory that was leaked after the issue of a set memory debug incremental starting-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

The following sections provide examples of output from the show memory debug leaks and show memory debug incremental commands:

Example: show memory debug leaks

Example: show memory debug leaks chunks

Example: show memory debug leaks largest

Example: show memory debug leaks summary

Example: show memory debug incremental allocations

Example: show memory debug incremental status

Example: show memory debug leaks

The following example shows output from the show memory debug leaks 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
 
   

Table 1 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 show memory debug leaks chunks 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)
 
   

Table 2 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 show memory debug leaks largest 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 show memory debug leaks largest 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 show memory debug leaks summary 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
 
   

Table 3 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 show memory debug incremental 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 show memory debug incremental 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

Table 4 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.


Note Table 4 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.


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)