PoolMon Examples
This topic includes the following examples of PoolMon use:
Example 1: Display and Sort PoolMon Output
Example 2: Display Driver Names
Example 3: Detect Memory Leakage
Example 4: Examine a Pool Memory Leak
Example 5: Monitor a Terminal Server Session
Example 1: Display and Sort PoolMon Output
This example describes various ways to configure the PoolMon display. By default, PoolMon displays all kernel memory allocations in alphanumeric order by tag value. You can modify the sort order of the display at the command line or while PoolMon is running.
The following command starts PoolMon:
poolmon
The following command starts PoolMon and sorts the display by number of free operations:
poolmon /f
While poolmon is running, you can use the run-time commands to change the display. For example, to sort the display by number of bytes used, press b. To sort by bytes per allocation, press m.
The following command starts PoolMon and displays only allocations from the nonpaged pool:
poolmon /p
While PoolMon is running, press p to toggle through allocations from the paged pool, the nonpaged pool, or both.
To start PoolMon and display data for allocations with a particular tag, use the /i parameter. The following command displays allocations with the AfdB tag (the tag used by afd.sys for data buffers).
poolmon /iAfdB
To exclude allocations with a particular tag, use the /x parameter. The following command displays all allocations that do not have the AfdB tag;
poolmon /xAfdB
You can use an asterisk (*) and/or a question mark (?) to specify a set of tags with the same characters. The following command displays allocations that have pool tags beginning with Afd, the tag used by afd.sys;
poolmon /iAfd*
A PoolMon startup command can include multiple /i and /x parameters. The following command displays allocations that have tags beginning with Aud and four-character tags beginning with Cc, except for allocations with the CcBc tag;
poolmon /iAud* /iCc?? /xCcBc
You can also sort the PoolMon display by the change in a value between updates. The /( parameter places PoolMon in sort-by-change mode.
The following command displays allocations with tags beginning with Afd, and sorts by the change in allocations. It uses the /a parameter to sort by number of allocations and the /) parameter to sort by the change in the number of allocations.
poolmon /iAfd* /( /a
The /( parameter and the parentheses keys are toggle switches. When PoolMon is in sort-by-change mode, it interprets all sort commands as commands to sort by the change in the value. If you press a parenthesis key again, it sorts by the value.
Example 2: Display Driver Names
You can use the PoolMon /g parameter to display the names of Windows components and commonly used drivers that assign each pool tag. If you find a problem in allocations with a particular tag, this feature helps you identify the offending component or driver.
The components and drivers are listed in the Mapped_Driver column, the right-most column in the display. The data for the Mapped_Driver column comes from pooltag.txt, a file installed with the WDK.
The following command displays memory allocated with tags that begin with NtF. (It uses the question mark character (?) as a wildcard.) The /g parameter adds the Mapped_Driver column.
poolmon /iNtF? /g "C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\triage\pooltag.txt"
You can also copy the pooltag.txt file to the same location as poolmon. This allows this usage.
poolmon /iNtF? /g
The resulting display lists allocations with tags beginning in NtF. The rightmost column in the display, Mapped_Driver, shows that the memory was allocated by ntfs.sys, the driver for the NTFS file system. In this case, the display is even more specific, because pooltag.txt includes the source files for NTFS allocations.
Memory: 260620K Avail: 65152K PageFlts: 85 InRam Krnl: 2116K P:19560K
Commit: 237688K Limit: 640916K Peak: 260632K Pool N: 8500K P:33024K
System pool information
Tag Type Allocs Frees Diff Bytes Per Alloc Mapped_Driver
NtFA Nonp 9112 ( 0) 9112 ( 0) 0 0 ( 0) 0 [ntfs.sys - AttrSup.c]
NtFB Paged 3996 ( 0) 3986 ( 0) 10 252088 ( 0) 25208 [ntfs.sys - BitmpSup.c]
NtFC Paged 1579279 ( 0) 1579269 ( 0) 10 640 ( 0) 64 [ntfs.sys - Create.c]
NtFD Nonp 13 ( 0) 13 ( 0) 0 0 ( 0) 0 [ntfs.sys - DevioSup.c]
NtFF Paged 1128 ( 0) 1128 ( 0) 0 0 ( 0) 0 [ntfs.sys - FileInfo.c]
NtFI Nonp 152 ( 0) 152 ( 0) 0 0 ( 0) 0 [ntfs.sys - IndexSup.c]
NtFL Nonp 68398 ( 0) 68390 ( 0) 8 27280 ( 0) 3410 [ntfs.sys - LogSup.c]
NtFS Paged 2915 ( 0) 2614 ( 0) 301 80192 ( 0) 266 [ntfs.sys - SecurSup.c]
NtFa Paged 838 ( 0) 829 ( 0) 9 288 ( 0) 32 [ntfs.sys - AllocSup.c]
NtFd Paged 137696 ( 0) 137688 ( 0) 8 720 ( 0) 90 [ntfs.sys - DirCtrl.c]
NtFf Nonp 2 ( 0) 1 ( 0) 1 40 ( 0) 40 [ntfs.sys - FsCtrl.c]
NtFs Nonp 48825 ( 0) 47226 ( 0) 1599 64536 ( 0) 40 [ntfs.sys - StrucSup.c]
NtFv Paged 551 ( 0) 551 ( 0) 0 0 ( 0) 0 [ntfs.sys - ViewSup.c]
Pooltag.txt is extensive, but it is not a complete list of all tags used in Windows. When a tag that appears in the display is not included in pooltag.txt, PoolMon displays "Unknown driver" in the Mapped_Driver column for the tag.
The following examples demonstrate this method on a 32 bit system.
The following command uses the /i parameter to list allocations with tags that end in MEM. The /g parameter adds the driver name to the display from the pooltag.txt file.
poolmon /i?MEM /g
The resulting display lists the allocations with tags ending in MEM. However, because the MEM tags are not included in pooltag.txt, "Unknown Driver" appears in the Mapped_Driver column in place of the driver name.
Tag Type Allocs Frees Diff Bytes Per Alloc Mapped_Driver
1MEM Nonp 1 ( 0) 0 ( 0) 1 3344 ( 0) 3344 Unknown Driver
2MEM Nonp 1 ( 0) 0 ( 0) 1 3944 ( 0) 3944 Unknown Driver
3MEM Nonp 3 ( 0) 0 ( 0) 3 248 ( 0) 82 Unknown Driver
The following command starts PoolMon. It uses the /i parameter to list allocations with tags ending in MEM.
poolmon /i?MEM
The following command lists allocations for tags beginning with Ip. It uses the /g parameter, which uses the contents of the pooltag.txt file in the Mapped_Driver column.
poolmon /iIp* /g
In the resulting display, the Mapped_Driver column contains data from the pooltag.txt files.
Memory: 130616K Avail: 23692K PageFlts: 146 InRam Krnl: 2108K P: 9532K
Commit: 187940K Limit: 318628K Peak: 192000K Pool N: 8372K P:13384K
System pool information
Tag Type Allocs Frees Diff Bytes Per Alloc Mapped_Driver
IpEQ Nonp 1 ( 0) 0 ( 0) 1 1808 ( 0) 1808 [ipsec][ipsec.sys - event queue]
IpFI Nonp 26 ( 0) 0 ( 0) 26 7408 ( 0) 284 [ipsec][ipsec.sys - Filter blocks]
IpHP Nonp 1 ( 0) 1 ( 0) 0 0 ( 0) 0 [ipsec.sys - IP Security]
IpIO Nonp 1 ( 0) 1 ( 0) 0 0 ( 0) 0 [ipsec]
IpLA Nonp 1 ( 0) 0 ( 0) 1 248 ( 0) 248 [ipsec][ipsec.sys - lookaside lists]
IpSH Nonp 1 ( 0) 1 ( 0) 0 0 ( 0) 0 [ipsec.sys - IP Security]
IpSI Nonp 1027 ( 0) 0 ( 0) 1027 53272 ( 0) 51 [ipsec][ipsec.sys - initial allcoations]
IpTI Nonp 3 ( 0) 0 ( 0) 3 5400 ( 0) 1800 [ipsec][ipsec.sys - timers]
Example 3: Detect Memory Leakage
This example suggests a procedure for using PoolMon to detect a memory leak.
Start PoolMon with the parameters /p /p (display only allocations from the paged pool) and /b (sort by the number of bytes).
poolmon /p /p /bLet PoolMon run for a few hours. Because starting PoolMon changes the data, it must regain a steady state before the data is reliable.
Save the information generated by PoolMon, either as a screen shot, or by copying it from the command window and pasting it into Notepad.
Returning to PoolMon, press the p key twice to display only allocations from the nonpaged pool.
Repeat steps 3 and 4 approximately every half-hour for at least two hours, switching between the paged and nonpaged pool displays each time.
When data collection is complete, examine the Diff (allocation operations minus free operations) and Bytes (number of bytes allocated minus number of bytes freed) values for each tag, and note any that continually increase.
Next, stop PoolMon, wait for a few hours, and then restart PoolMon.
Examine the allocations that were increasing, and determine whether the bytes are now freed. The likely cause is allocations that have still not been freed or have continued to increase in size.
Example 4: Examine a Pool Memory Leak
The following example demonstrates using PoolMon to investigate a pool memory leak from a suspected printer driver. In this example, PoolMon displays data that Windows collects about memory allocations with the Dsrd tag.
Some printer drivers assign the Drsd tag when they allocate Graphical Device Interface (GDI) objects and associated memory. If a printer driver has an object leak, the memory allocated with the Drsd tag also will leak.
Note Before running the steps in this example, ensure that the printer you are using will not be interrupted until you are finished. Otherwise, the results may be invalid.
At the command line, type the following:
poolmon /iDrsd
This command directs PoolMon to display information for allocations with the Drsd tag. (Pool tags are case-sensitive, so be sure to type the command exactly as shown.)
Record the values in the Diff and Bytes columns. In the following sample display, the value of Diff is 21 and the number of Bytes is 17472.
Memory: 130480K Avail: 91856K PageFlts: 1220 InRam Krnl: 2484K P: 7988K
Commit: 30104K Limit: 248432K Peak: 34028K Pool N: 2224K P: 8004K
Tag Type Allocs Frees Diff Bytes Per Alloc
Drsd Paged 560 ( 177) 539 ( 171) 21 17472 ( 4992) 832
Send a job to the printer, wait briefly for Windows to return to normal, and then record the values for the Diff and Bytes columns.
Memory: 130480K Avail: 91808K PageFlts: 1240 InRam Krnl: 2488K P: 7996K
Commit: 30152K Limit: 248432K Peak: 34052K Pool N: 2224K P: 8012K
Tag Type Allocs Frees Diff Bytes Per Alloc
Drsd Paged 737 ( 0) 710 ( 0) 27 22464 ( 0) 832
When the memory management for the printer driver is working properly, the value of Diff should return to its original value of 21 after printing. However, as the preceding output illustrates, the value of Diff rose to 27, and the number of Bytes rose to 22464. The difference between the initial and subsequent output means that six Drsd blocks, with a total of 4992 bytes, leaked during printing.
For More Information
If you believe you have identified a leaking driver, go to the Microsoft support website and search the Knowledge Base for relevant articles, or contact the vendor if this is a third party driver.
Example 5: Monitor a Terminal Server Session
This example shows several ways to display allocations from the Terminal Services session pools. It demonstrates the use of the /s command-line parameter, and the s, TSSessionID, and i running parameters.
The following command displays allocations from all of the Terminal Services session pools. In this example, the local computer, which is configured as a Terminal Server, is hosting the sessions, and client computers are using the Remote Desktop feature to connect to the host.
poolmon /s
In response, PoolMon displays allocations from all session pools. Note the "All sessions pool information" title in the header.
Memory: 523572K Avail: 233036K PageFlts: 344 InRam Krnl: 1828K P:18380K
Commit: 193632K Limit:1279764K Peak: 987356K Pool N:14332K P:18644K
All sessions pool information
Tag Type Allocs Frees Diff Bytes Per Alloc
Bmfd Paged 361 ( 0) 336 ( 0) 25 57832 ( 0) 2313
DDfb Paged 34 ( 0) 22 ( 0) 12 720 ( 0) 60
Dddp Paged 8 ( 0) 6 ( 0) 2 272 ( 0) 136
Dh 1 Paged 24 ( 0) 24 ( 0) 0 0 ( 0) 0
Dh 2 Paged 344 ( 0) 344 ( 0) 0 0 ( 0) 0
Dvgr Paged 2 ( 0) 2 ( 0) 0 0 ( 0) 0
GDev Paged 108 ( 0) 102 ( 0) 6 20272 ( 0) 3378
GFil Paged 29 ( 0) 27 ( 0) 2 160 ( 0) 80
GPal Paged 11 ( 0) 8 ( 0) 3 816 ( 0) 272
GTmp Paged 88876 ( 1) 88876 ( 1) 0 0 ( 0) 0
GUma Paged 2 ( 0) 2 ( 0) 0 0 ( 0) 0
Galp Paged 3250 ( 0) 3250 ( 0) 0 0 ( 0) 0
Gbaf Paged 9829 ( 0) 9801 ( 0) 28 19712 ( 0) 704
Gcac Paged 3761 ( 0) 3706 ( 0) 55 288968 ( 0) 5253
Gcsl Paged 1 ( 0) 0 ( 0) 1 488 ( 0) 488
Gdbr Paged 6277 ( 0) 6271 ( 0) 6 1872 ( 0) 312
...
To see allocations from a particular session pool, type the session ID immediately after the /s parameter, as shown in the following command. This command displays session pool allocations for Terminal Services session 0.
poolmon /s0
In response, PoolMon displays allocations from the session pool for Terminal Services session 0. Note the "Session 0 pool information" title in the header.
Memory: 523572K Avail: 233024K PageFlts: 525 InRam Krnl: 1828K P:18384K
Commit: 193760K Limit:1279764K Peak: 987356K Pool N:14340K P:18644K
Session 0 pool information
Tag Type Allocs Frees Diff Bytes Per Alloc
Bmfd Paged 361 ( 0) 336 ( 0) 25 57832 ( 0) 2313
DDfb Paged 34 ( 0) 22 ( 0) 12 720 ( 0) 60
Dddp Paged 8 ( 0) 6 ( 0) 2 272 ( 0) 136
Dh 1 Paged 24 ( 0) 24 ( 0) 0 0 ( 0) 0
Dh 2 Paged 344 ( 0) 344 ( 0) 0 0 ( 0) 0
Dvgr Paged 2 ( 0) 2 ( 0) 0 0 ( 0) 0
GDev Paged 108 ( 0) 102 ( 0) 6 20272 ( 0) 3378
GFil Paged 29 ( 0) 27 ( 0) 2 160 ( 0) 80
GPal Paged 11 ( 0) 8 ( 0) 3 816 ( 0) 272
GTmp Paged 89079 ( 99) 89079 ( 99) 0 0 ( 0) 0
GUma Paged 2 ( 0) 2 ( 0) 0 0 ( 0) 0
Galp Paged 3250 ( 0) 3250 ( 0) 0 0 ( 0) 0
Gbaf Paged 9830 ( 0) 9802 ( 0) 28 19712 ( 0) 704
Gcac Paged 3762 ( 0) 3707 ( 0) 55 283632 ( 0) 5156
Gcsl Paged 1 ( 0) 0 ( 0) 1 488 ( 0) 488
Gdbr Paged 6280 ( 0) 6274 ( 0) 6 1872 ( 0) 312
...
To help determine which drivers and components are allocating memory from the session pool, add the /g parameter, as shown in the following command. The /g parameter adds a Mapped_Driver column listing the Windows components and drivers that assign each tag.
poolmon /s0 /g
Memory: 523572K Avail: 235876K PageFlts: 43 InRam Krnl: 1900K P:18860K
Commit: 185040K Limit:1279764K Peak: 987356K Pool N:14684K P:19124K
Session 0 pool information
Tag Type Allocs Frees Diff Bytes Per Alloc Mapped_Driver
Bmfd Paged 421 ( 0) 396 ( 0) 25 57832 ( 0) 2313 [Font related stuff]
DDfb Paged 34 ( 0) 22 ( 0) 12 720 ( 0) 60 Unknown Driver
Dddp Paged 11 ( 0) 6 ( 0) 5 392 ( 0) 78 Unknown Driver
Dh 1 Paged 37 ( 0) 35 ( 0) 2 224 ( 0) 112 Unknown Driver
Dh 2 Paged 367 ( 0) 364 ( 0) 3 912 ( 0) 304 Unknown Driver
Dvgr Paged 2 ( 0) 2 ( 0) 0 0 ( 0) 0 [vga for risc video driver]
GDev Paged 119 ( 0) 113 ( 0) 6 20272 ( 0) 3378 [Gdi pdev]
GFil Paged 29 ( 0) 27 ( 0) 2 160 ( 0) 80 [Gdi engine descriptor list]
GPal Paged 11 ( 0) 8 ( 0) 3 816 ( 0) 272 [Gdi Objects]
GTmp Paged 98626 ( 1) 98626 ( 1) 0 0 ( 0) 0 [Gdi Objects]
GUma Paged 2 ( 0) 2 ( 0) 0 0 ( 0) 0 [Gdi Objects]
Galp Paged 3250 ( 0) 3250 ( 0) 0 0 ( 0) 0 [Gdi Objects]
Gbaf Paged 10331 ( 0) 10305 ( 0) 26 18304 ( 0) 704 [Gdi Objects]
Gcac Paged 4722 ( 0) 4666 ( 0) 56 305400 ( 0) 5453 [Gdi glyph cache]
Gcsl Paged 1 ( 0) 0 ( 0) 1 488 ( 0) 488 [Gdi string resource script names]
Gdbr Paged 6972 ( 0) 6965 ( 0) 7 2184 ( 0) 312 [Gdi driver brush realization]
You can also configure the Terminal Services session pool display while PoolMon is running. The following table shows a series of running commands, in the order in which they are typed, and the resulting PoolMon display.
The series begins with a command to start PoolMon. All other parameters are typed while PoolMon is running.
poolmon
| Key | Result | Description |
|---|---|---|
s |
Displays all session pools. |
|
s |
Displays the system pools. |
The s parameter toggles the display between the system pools and the Terminal Services session pools. |
0 |
Displays session 0 pool. |
You can type a session ID while displaying the system pools. |
7 |
Displays session 7 pool. |
|
a |
Displays pool allocations for session 7, sorted by number of allocations. |
All standard running parameters are valid for session pool displays. |
0 |
Displays allocations for session 0, sorted by number of allocations. |
Session and sorting options are retained until changed. |
s |
Displays the system pools. |
|
s |
Displays allocations for session 0, sorted by number of allocations. |
Session option is retained. |
10ENTER |
Displays Session 1 allocations, and then displays Session 0 allocations. |
Without i, you can enter only session IDs 0 through 9. |
i |
Prompts for a Terminal Server session ID. |
|
10 |
Displays Session 10 allocations. |
|
i |
Prompts for a Terminal Server session ID. |
To display all session pools, press i and then press ENTER. |
ENTER |
Displays all session pools. |
Only systems configured as a Terminal Server allocate memory from the session pool. If you use PoolMon to display the session pool on a computer that is not a Terminal Server, or if you type a session ID that does not exist on Windows, PoolMon does not display any allocations. Instead, it displays only the headings with general memory data.
The following command displays allocations from all Terminal Services session pools:
poolmon /s
The following figure shows the PoolMon display that would result if the /s command were submitted to a computer running Windows XP that could not be configured as a Terminal Server:
Memory: 260620K Avail: 44956K PageFlts: 308 InRam Krnl: 2744K P:20444K
Commit: 185452K Limit: 640872K Peak: 192472K Pool N: 8112K P:20648K
All sessions pool information
Tag Type Allocs Frees Diff Bytes Per Alloc