Slaying the Virtual Memory Monster – Part II

Someday I’ll learn to write a simple blog post—a couple of paragraphs about something cool and edgy.  Not today.  There is no way to cover Virtual Memory in brevity and still get anything out of it so... we’re going to trudge through this.  In my last post, we covered some important VM fundamentals.  In this post, we’re going to get a little more “hands on” and actionable.

Let’s talk about ways to diagnose and deal with VM issues.  Because the failure characteristics are somewhat “random” in nature and there are several ways to tackle them, the first step is to profile the VM space on the device and try to figure out what you are up against.  This is a good thing to do for a number of reasons:
   1)  You need know which processes are the biggest consumers of VM space reserved for loading DLLs
   2)  You need to know how much VM space is still available inside YOUR process
   3)  How you attack a VM problem depends on #1 and #2 above

Profiling the Virtual Memory Situation

When I first started debugging VM issues on Windows Mobile, I was surprised to find that we didn’t release any decent low level memory tools in the public WM SDK.  There are a couple of OEM tools we provide to device makers, but since they are not included in the public SDK, they won’t help us much and I’m not going to use or discuss them here.  The good news is that the basic APIs you need to understand VM use are publically exposed within the ToolHelp API set.  These APIs work across all versions of the WM platforms and for the most part – this technique gets the job done.  The best way to get started with this approach is via and old support tool we released way back in 2002 which remains available in our downloads -- called DumpMem.  DumpMem simply uses the ToolHelp APIs to dump information about all the running processes into a text file and includes some basic heap data.  The files are not particularly fun to work with (it’s a big messy text file), but I’ve seen several versions of home grown tools built around the underlying DumpMem code and parsing tools for the logs.  I’ve written several myself.  With a little practice, you can learn to make sense of these files and gain a lot of insight from them.

One concept I didn’t cover in the last post was “slots”.  A slot is a basic unit for maintaining virtual memory within the Windows Embedded CE kernel.  Without going into great detail, I’ll just say that each slot in the user address space is 32 MB and there are 32 slots set aside for the maximum number of running process.  Two slots are special.  Slot 0 is used for the current running process and Slot 1 is reserved exclusively for in-ROM components that have been included as part of the device image.  Slot 0 is represented by the area below 0x02000000 and since it’s where the active process runs, that’s what we’re most interested in.  For all practical purposes, that’s our 32MB virtual address space area we have to make it all work.


Virtual Memory in a “perfect world”

Our emulators are a good place to start.  They don’t have the OEM extras -- code, drivers, startup software, etc., and thus, generally have more free VM than you’ll find on commercially available devices. 

What are we looking for?

1)      First we want to know where the lowest DLL is loaded in memory (regardless of process). 
Since we established that every DLL has to load lower than previous DLLs, we’re basically looking to see how far that load position has gotten pushed down.  All running processes that load DLLs can contribute to this position.  This is often the biggest contributor in VM failure scenarios.  When the DLL load position get pushed really low, it’s more likely to bump into a process heap (which is growing upward).  When that happens, LoadLibrary fails and you won’t be able to load any more components in your process.  This is also a very important metric to consider for all processes since the same low DLL load position has implications for all apps.

2)      Next we want to identify the biggest free area between our heap (growing upward) and the lowest DLL load position in our process. 
We want to know this because it tells us how much room is left to load DLLs in our process and is often the largest single piece of contiguous memory left for the heap (important if you need to allocate a sizable chunk of memory without going to the large memory area like an image, etc).

Step by Step –  Create a Memory Dump using DumpMem

Let’s start with DumpMem and a “Hello World” application.  I’m just going to let Visual Studio build a simple “Hello World” application and launch it on the WM6 Professional emulator.  Then I’ll use DumpMem to dump the process and we’ll get messy. 


I simply select the process I want to dump (HelloWorld_1), choose “Create File” and dumpmem writes everything into a file called “dumpmem.txt” in the root directory of the device.  You can choose any process in the list, but DumpMem only grabs extra heap information for the specific you select.  We’re not going to use heap data for this exercise, but sometimes, it’s good to see what kind of allocations are in there.

*DumpMem uses a fairly memory intensive API called CreateToolhelp32Snapshot to grab heap info about the selected process.  If VM is already very tight on the device you are profiling, this API can cause DumpMem to fail.  If this happens, you can change the call in the DumpMem source to pass in TH32CS_SNAPNOHEAPS flag.  This won’t give you a dump of the actual heap data, but it will allow you to get the process info with all the loaded modules which is usually all you need.

The DumpMem log is broken into several sections:

·        Platform Information

o   This is simply the platform, CPU type, and version number

·        Virtual Memory Dump (of the selected process)

o   This is a map of the 32MB process space for the selected application.  The format is address, size, state, type, use. 

·        Heap Dump of the selected process

o   The heap(s) break down every chunk of raw heap memory it contains and shows you the address, size of the chunk, and if it’s in use (fixed or free)

·        Processes and their modules

o   An enumeration of all the running processes, all the components each has loaded, and then for each component – the name, load address, size, and module attributes


We’ll go into these sections in more detail later on, but first let’s just focus on our first goal – identifying the lowest DLL load position.  To do this, skip over all the sections in the log file you just created to the last one – “Processes and their modules”.

What you find here is a list of all the running processes and more importantly – all the components (DLLs, MUIs, etc.) they have loaded along with their load positions.  We’re mostly interested in components that are loaded into Slot 0 (below 0x02000000).  One quick way to identify these components is by their attribute in the list.  If the attribute does not include “XIP” we want to pay special attention because they will always be in this space and usually one of the lowest DLLs in memory (see bold items below).  Another way might be to look at the load position of each component in something like Remote Process Viewer and see if it’s using loading below 0x2000000.  If the component has an XIP attribute, then it’s a ROM based module and usually loaded into a special area in Slot 1 (outside the area we’re worried about).  Sometimes, when the XIP region gets full, these components will start getting pushed down into Slot 0.  When that happens, they affect our VM space the same way as non-XIP components.  Anything below 0x02000000 that is not labeled XIP is what we’re primarily concerned about.  If I look at the dumpmem.txt file I just created, that section looks something like the list below (I’ve trimmed off each module list after the first 3-4 items).

Processes and their Modules

Module File Attributes Legend

RO - Read Only

H - Hidden

S - System

A - Archive

C - Compressed


NK.EXE base address: C2000000


    coredll.dll 03F4E000    96000 RO, H, S, XIP

coredll.dll.0409.mui 7FFE0000    15000 RO, S, XIP

         hd.dll 88079000     4000 RO, H, S, XIP



filesys.exe base address: 04000000


     rsaenh.dll 01930000    2B000 RO, H, S, C, RAM from ROM

     vcefsd.dll 01990000    1C000 RO, H, S, XIP

     ramfmd.dll 01A80000     9000 RO, H, S, XIP



device.exe base address: 06000000


     rsaenh.dll 01930000    2B000 RO, H, S, C, RAM from ROM

serial_smdk2410.dll 019E0000     A000 RO, H, S, XIP

     serdma.dll 01A10000     7000 RO, S, XIP




services.exe base address: 08000000


     lap_pw.dll 01910000    18000 RO, S, C, RAM from ROM

     rsaenh.dll 01930000    2B000 RO, H, S, C, RAM from ROM

   obexsrvr.dll 02416000     A000 RO, H, S, XIP



gwes.exe base address: 0A000000


   kbdmouse.dll 01960000     9000 RO, H, S, XIP

      touch.dll 019B0000     A000 RO, H, S, XIP

deviceemulator_lcd.dll 01B30000    2D000 RO, H, S, XIP




shell32.exe base address: 0C000000


wlmhssearchbarcode.dll 01890000     8000 RO, S, C, RAM from ROM

  wlmshared.dll 018A0000    3C000 RO, S, C, RAM from ROM

wlmuiframework.dll 018E0000    19000 RO, S, C, RAM from ROM

wlmtodayscreen.dll 01900000     6000 RO, S, C, RAM from ROM

    siminit.dll 02090000     6000 RO, S, XIP



EmulatorStub.exe base address: 0E000000


    coredll.dll 03F4E000    96000 RO, H, S, XIP

coredll.dll.0409.mui 7FFE0000    15000 RO, S, XIP



poutlook.exe base address: 10000000


     ossvcs.dll 0300E000    42000 RO, S, XIP

   oleaut32.dll 03050000    2F000 RO, H, S, XIP

      ole32.dll 0307F000    2C000 RO, H, S, XIP



connmgr.exe base address: 12000000


     rsaenh.dll 01930000    2B000 RO, H, S, C, RAM from ROM

        ril.dll 02096000    11000 RO, S, XIP

   cspvoice.dll 02125000    10000 RO, S, XIP



ConManClient2.exe base address: 14000000


  devicedma.dll 01860000     B000 A

     edbgtl.dll 01870000    14000 A

    coredll.dll 03F4E000    96000 RO, H, S, XIP



HelloWorld_1.exe base address: 16000000


 mscoree2_0.dll 01C70000    C4000 RO, H, S, XIP

netcfagl2_0.dll 0218C000    3B000 RO, H, S, XIP

    mscoree.dll 021C7000    10000 RO, H, S, XIP




fexplore.exe base address: 18000000


     ossvcs.dll 0300E000    42000 RO, S, XIP

   oleaut32.dll 03050000    2F000 RO, H, S, XIP

      ole32.dll 0307F000    2C000 RO, H, S, XIP



dumpmem.exe base address: 1A000000


   toolhelp.dll 02E5F000     4000 RO, H, S, XIP

     ossvcs.dll 0300E000    42000 RO, S, XIP

   oleaut32.dll 03050000    2F000 RO, H, S, XIP




Step by Step – Build a list of the DLLs loaded below 0x02000000

If you make a list of all the DLLs in every process that have been loaded under 0x02000000 and order them by load position in memory, you get a pretty good idea of what’s going on with the low DLL load position and which processes have contributed to pushing it down to its current position.  Our current list of all DLLs loaded under 0x02000000 looks like this:


Component –––––––––––––––– load position – size -- attributes

  devicedma.dll                   01860000     B000 A  (lowest DLL in memory)

     edbgtl.dll                         01870000    14000 A

wlmhssearchbarcode.dll  01890000     8000 RO, S, C, RAM from ROM

  wlmshared.dll                   018A0000    3C000 RO, S, C, RAM from ROM

wlmuiframework.dll         018E0000    19000 RO, S, C, RAM from ROM

wlmtodayscreen.dll          01900000     6000 RO, S, C, RAM from ROM

     lap_pw.dll                      01910000    18000 RO, S, C, RAM from ROM

     rsaenh.dll                       01930000    2B000 RO, H, S, C, RAM from ROM

   kbdmouse.dll                                 01960000     9000 RO, H, S, XIP

      touch.dll                                      019B0000     A000 RO, H, S, XIP

serial_smdk2410.dll                        019E0000     A000 RO, H, S, XIP

     serdma.dll                                    01A10000     7000 RO, S, XIP

s3c2410x_wavedev.dll                   01A20000     9000 RO, H, S, XIP

 pwrbtn2410.dll                               01A90000     4000 RO, H, S, XIP

     pcmcia.dll                                     01AA0000     A000 RO, H, S, XIP

pcc_smdk2410.dll                            01AB0000     9000 RO, H, S, XIP

   pcc_serv.dll                                    01AC0000     F000 RO, H, S, XIP

    nullcam.dll                                    01AD0000     C000 RO, H, S, XIP

   nleddrvr.dll                                     01AE0000     4000 RO, H, S, XIP

      irsir.dll                                          01B00000     6000 RO, H, S, XIP

   emulserv.dll                                   01B10000     5000 RO, H, S, XIP

   dmatrans.dll                                  01B20000     5000 RO, H, S, XIP

   battdrvr.dll                                     01BF0000     5000 RO, H, S, XIP

  backlight.dll                                    01C00000     4000 RO, H, S, XIP

   asyncmac.dll                                  01C20000     6000 RO, H, S, XIP

      scard.dll                                       01C40000     B000 RO, H, S, XIP

 mscoree2_0.dll                               01C70000    C4000 RO, H, S, XIP



Step by Step – Analyze the memory data as it applies to your process

Low DLL load position

This is a pretty small list of DLLs using a simple environment (it’s the WM 6.0 SDK refresh Pro emulator).  You can see the lowest DLL (devicedma.dll) loaded at 0x01860000 (~24MB).   You may also notice that if you add the DLL size to a load position, there may be a small gap before the next DLL loads in memory.  In WM5, we had to load components on a 64K boundary.  This means even if you loaded two DLLs that were 10K in size, they would eat up 128K of VM.  In WM6, we use a 4K boundary which makes more efficient use of memory.

From our data, it appears that the next DLL loaded into memory (from any process) is going to find a home right under 0x01860000.  That’s where the lowest module is loaded right now and the next one has to load underneath it.  This answers our first question about where the low DLL load position is.  As you can see, we’re already a long way down from 32MB since this is ~24 MB in the VM map.  The low DLL load mark has already been reduced by 8MB.  What pushed it down that far?

You could go back through the list of component under 0x02000000 and find the processes that loaded them.  That would tell you which processes are the biggest culprits.  If you did this, you would see that shell32.exe is responsible for loading several Windows Mobile Live components, but even so – the largest one is only about 240K.  The real culprits are all the system components and drivers that have been pushed down into Slot 0 because slot 1 was full.  This is very typical of commercial devices.  That’s what pushed down the low DLL load position by 8MB.   This number is highly variable for retail devices and something you typically don’t have a lot of control over.  It’s also why if you have a big application that requires a lot of VM space to load DLLs, you need to be especially careful to profile your target devices.

What about our heap space?

To get an understanding of available heap space left, I usually look at the first section of the dumpmem.txt file called “Virtual Memory Dump” (left column below).    This is a simple outline of your memory space and how it’s being used.  If I identify the heap area between where my EXE is loaded and before the first DLLs appear in this VM Map, I can find the largest available free memory area left in my process. 

Before we look at the virtual memory dump, let’s clarify one point.  You will notice that all the memory positions seem to be offset from 0x16000000.  You may recall that the base address for HelloWorld_1 was 0x16000000 (where it lives when it’s not the active process in slot 0).  Just subtract 16000000 from all the memory positions if it’s easier to think about it in the context of Slot 0.  Here we go…

Virtual Memory Dump of HelloWorld_1.exe


16000000    10000 F NA

*The first little block of memory is 10000 in size.  This is the reserved position at the bottom of each process and will always be here for any process.

Next comes our EXE…


16010000     2000 R NA Image

16012000     1000 C RW Image

16013000     1000 R NA Image

16014000     1000 C RO Image

16015000     1000 R NA Image

16016000     1000 C RO Image

16017000     1000 R NA Image

*The memory from 16010000-16017000 is labeled as “image”.  This is the bottom of the VM position and where our EXE is loaded.   The lowest section labeled “Image” is always your EXE.

Next comes our Heap and Stack memory…


16018000     8000 F NA

16020000     1000 C RW Private

16021000     F000 F NA

16030000     D000 R NA Private

1603D000     3000 C RW Private

16040000     5000 C RW Private

16045000    2A000 R NA Private

1606F000     1000 F NA

16070000     5000 C RW Private

16075000    2A000 R NA Private

1609F000     1000 F NA

160A0000     D000 C RW Private

160AD000    22000 R NA Private

160CF000     1000 F NA

160D0000    20000 C RW Private

160F0000     F000 R NA Private

160FF000     1000 F NA

16100000     1000 C RW Private

16101000    2E000 R NA Private

1612F000     1000 F NA

16130000     F000 R NA Private

1613F000     1000 C RW Private

16140000    10000 C RW Private

16150000     F000 R NA Private

1615F000     1000 C RW Private

*The area from 1601800-1615F000 is dynamic memory being used by the process – heap, stack, etc.  Notice there are a few free areas marked “F” but most of it is “Private” memory which has been committed or reserved.  This is where the majority of your dynamic memory allocations occur and your heap expands upward.


16160000  1B10000 F NA

*At the top of your heap area you will usually find a big free chunk of memory.  This is largest contiguous free chunk of memory available inside your VM space (Slot 0).  In this case, it’s 1B10000 or ~27MB.

Next (at the top of the VM area working its way down) you will find any DLLs loaded in our process.  The first one shows up at 0x17C70000…


17C70000     1000 R NA Image

17C71000     7000 C RO Image

17C78000     1000 R NA Image

17C79000     3000 C RO Image

17C7C000    18000 R NA Image

17C94000    1E000 C RO Image

17CB2000     1000 R NA Image

17CB3000    14000 C RO Image

17CC7000     1000 R NA Image

17CC8000    12000 C RO Image

17CDA000     5000 R NA Image

17CDF000     3000 C RO Image

17CE2000     4000 R NA Image

17CE6000     1000 C RO Image

17CE7000     5000 R NA Image

17CEC000     6000 C RO Image

17CF2000     4000 R NA Image

17CF6000     1000 C RO Image

17CF7000     9000 R NA Image

17D00000     4000 C RO Image

17D04000     4000 R NA Image

17D08000     2000 C RO Image

17D0A000     2000 R NA Image

17D0C000     B000 C RO Image

17D17000     1000 R NA Image

17D18000     2000 C RO Image

17D1A000     1000 R NA Image

17D1B000     1000 C RO Image

17D1C000     1000 R NA Image

17D1D000     1000 C RO Image

17D1E000     3000 R NA Image

17D21000     1000 C RO Image

17D22000     1000 R NA Image

17D23000     2000 C RO Image

17D25000     2000 R NA Image

17D27000     5000 C RW Image

17D2C000     8000 R NA Image

17D34000    EC000 F NA

17E20000    14000 R NA Image

17E34000     2000 C RW Image

17E36000    1A000 R NA Image

17E50000     1000 C RW Image

17E51000    53000 R NA Image

17EA4000     1000 C RW Image

17EA5000    58000 R NA Image

17EFD000     1000 C RW Image

17EFE000     8000 R NA Image

17F06000     5000 C RW Image

17F0B000    10000 R NA Image

17F1B000     1000 C RW Image

17F1C000    1A000 R NA Image

17F36000     1000 C RW Image

17F37000     E000 R NA Image

17F45000     1000 C RW Image

17F46000    1C000 R NA Image

17F62000     1000 C RW Image

17F63000     5000 R NA Image

17F68000     1000 C RW Image

17F69000     3000 R NA Image

17F6C000     2000 C RW Image

17F6E000    32000 R NA Image

17FA0000    40000 F NA

17FE0000    1C000 R NA Image

17FFC000     1000 C RW Image

17FFD000     3000 R NA Image

*Memory from 17C70000 up is labeled as “image”.   This is memory used by DLLs – remember they load from the top of the VM space and work their way down.  All I care about at this point is the lowest position used in my process.  If I map address lowest DLL loaded at 17C70000 back into Slot 0 (subtracting the base address), I get 1C70000 which can be easily identified as mscoree2_0.dll in the module section of HelloWorld.exe.


From this information, we achieve our second goal.  We know that there is a large free chunk of VM space (0x01B10000 bytes –or- ~27MB), between our EXE and the lowest DLL in our process.  The lowest DLL loaded into our process is mscoree2_0.dll at 0x01C70000.   


Making sense of it all

Let’s now regroup on our objectives and put it all in context.  Our goals were:

1)      Understanding the lowest DLL load position in all processes:
>>> devicedma.dll at position 0x01860000 (~24MB)   

2)      Identifying the largest chunk of available VM and lowest DLL in OUR process
>>> we found 0x1b10000 bytes FREE right above our heap and we located mscoree2_0.dll at 1C70000 giving us about 27MB of free space to work with.

This was simply example and done in a very clean environment so we’re still in a pretty healthy situation.  Goal #2 tells us we have plenty of space to grow (heap) and plenty of room to load more DLLs. 

Goal #1: The lowest DLL load position in OUR process is 0x1C70000 so you might expect the next DLL to load right under it.  Considering #1 though, the next DLL would actually load significantly lower – just below 0x01860000.  Remember that when our process loads another component, it has to find a position under every other component that has already been loaded by any process.  This, in effect, restricts our heap range a bit.  Where we had a giant contiguous chunk of almost 27MB worth of VM space—loading a component now would split up that area by positioning itself around 23-24MB in the map.  Our heap can still grow upward and claim most of this available space, but it’s no longer single contiguous chunk.  This becomes important when you have an app that might need to make a big allocation (e.g. – manipulating an image, media file, etc.).  I say "most" of this space because if you are not running with full privileges (e.g. - untrusted on a 2-tier phone), then you are limited to available VM space under the low DLL load position -- even if there is plenty of free space up there!

This is a really simple exercise, but you can imagine how complex this can get with a lot of applications running – especially if they load a bunch of other components.  While there may only be 32 processes running, don’t forget that services.exe and driver.exe can become quite full with dlls that load on boot.  This can contribute to pushing down that low DLL load position.   Once the DLL position gets pushed WAY down, the available area left to grow your heaps can get quite constrained.  If you start running into problems with VM issues or need to get an idea of what is going on, you can use the above techniques to get an idea of what you have to work with (and why it might be failing).

Where’s the smoking gun?

We already noted that when applications experience VM related failures, there’s not always a smoking gun.  The failures can be appear quite random.  Let’s talk about some of the most common failures and contributors.

Components that fail to load - The most common failure occurs when an application attempts to load a dependant component – either on startup or through a call to LoadLibrary.  There has to be enough space between your heap and the low DLL load position to succeed, so when the DLL load position gets pushed too far down, LoadLibrary will fail.  At this point, an application can fail to start or a manual call to LoadLibrary will return an error.  The actual affect on an application can vary depending on how it handles this failure.

Memory allocations that fail - When a heap can no longer expand, memory becomes too fragmented, or there is insufficient space for a large contiguous allocation-- memory allocations can begin fail.  Few developers write to code to adequately check for memory failures so this very often results in unhandled exceptions for the application (e.g. – crash).

Dynamic failures - It’s pretty easy to take responsibility for problems in your own application—failure to start, exceptions, etc., but it’s even more complex that.  VM problems commonly extend into other processes because of the DLL loading and memory rules.  How does this happen?

Because every process can contribute to the low DLL load position, this means that the order in which they start can make a big difference.  Suppose the low DLL load position has been pushed down to the point where only 10MB of space is left to load more DLLs.  What happens then if you have three application—“A”, “B”, and “C” that all load 5MB worth of unique components.  If you load “A” and “B”, then “C” fails.  If you load “B” and “C”, then “A” would fail. 

Part of the challenge today is that VM health is very much a little ecosystem with many contributors.  The OEM shares responsible for delivering a device that doesn’t eat up all the VM space before you install the first app.  The developer shares responsible for not taking more than their share of resources.  The end user shares responsible for all the apps they install.  Microsoft shares responsibility for mitigating this problem at a platform level so nobody has think about it.  In the not so distant future, we will likely adopt changes in the platform (like we did with CE6) that expand the VM range so that this isn’t an issue anymore.  Right now, we have to work with what we have.

Tactics developers use to address VM problems

·        Profile the VM space first.  You cannot solve this problem unless you know what is going on with your memory.

·        Static linking is your friend.  When you statically link code, it becomes part of thee EXE which means it loads in the bottom of the VM space (the best possible area).  You don’t have to worry about DLL load rules and you don’t impact the VM of other processes.  You may end up using a little more RAM if multiple apps use the same code, but the trade-off is probably worth the headaches you can avoid.  Plus, you avoid extra signing costs by eliminating DLLs.

·        Start order matters.  While more of a band-aid than a solution, controlling the load order of processes on a device can help you work around VM issues.  For this to work, you really need a good understanding of the memory profile of the device as well as which processes are contributing to the problem.  The first app gets the most DLL space, the second gets the slightly less, etc.  By controlling which apps start first and/or disabling services or drivers you don’t need – you can sometimes avoid VM problems.

·        Merge small DLLs.  Windows Mobile 5.0 had to load components on a 64K boundary which meant that every a small DLL used a minimum of 64K.  If you have a bunch of small DLLs, it may make sense to merge them to save space.  Windows Mobile 6 loads on a 4K boundary which makes much better use of space. 

·        Move resources to resource-only DLLs (dll’s with no entry point).  Resource only DLLs are loaded up in slot 63 and don’t use up your valuable VM space in slot 0.

·        For large memory allocations, consider using VirtualAlloc and the Large Memory Area (aka – High Memory Area).  Allocations of 2MB or greater use space well outside of slot 0 and leave your process with more room to work.

·        Trim your code.  Make it smaller and lighter and save on VM space


In Summary

I’ve rambled long enough about the Virtual Memory Monster.  Somewhere this is a blog post turned into whitepaper.  Hopefully those of you who read this now have a better understanding of the creature and some skills you can use to battle it.  Like most nasty, bad-guy type, it’s more misunderstood than evil.  Hopefully you never run into it, but if you do – you have some tools under your belt.

If you guys want to dig into this in more detail, let me know.  I could blog through a real world problem or two to help you get the hang of it. 

Some of you will undoubtedly want to know more about how NETCF optimizes memory inside of this limited area.  You will notice that if you load a NETCF assembly, it doesn’t use up DLL space like native DLLs.  NETCF goes to great lengths to make good use of memory transparently.  Since there are already some great posts on this topic, I’ll simply reference them here:

Next up…. Power Management or maybe IE Mobile?  Both of these areas seem to be generating a lot of interesting support activity right now.




Comments (18)
  1. I know a lot of users have come across memory issues especially when using the camera on your Windows

  2. If you are developing for Windows Mobile hopefully you’ve never encountered issues around Virtual Memory.

  3. Subtitles: – OutOfMemoryException (OOM) – SqlCeException: Not enough memory to complete this operation

  4. Subtitles: – OutOfMemoryException (OOM) – SqlCeException: Not enough memory to complete this operation

  5. I didn’t learn about Reed & Steve’s blog until today, but got there by learning about these posts:

  6. I didn't learn about Reed & Steve's blog until today, but got there by learning about these

  7. Over the years, I’ve delivered several “Top 10” sessions and called it different things.

  8. Thanks for attending my MSDN Webcast today “Top Developer Tips for Windows Mobile” . As promised, here

  9.     Previous post: Twisted Pixels – A Mobile Game Development Diary (Day 1) Doing Graphics

  10. Previous post: Twisted Pixels #2: Doing Graphics! What’s going on? To recap – I have a program that works

  11. Previous post: Twisted Pixels #2: Doing Graphics! What’s going on? To recap – I have a program that works

  12. Vino says:


    Thanks for the good post.

    I used the same techniques but could not figure out which is the lowest DLL that is loaded like the way you figured out mscoree2_0.dll.

    Since you already mentioned that you could take up a real world example, I have a dumpmem.txt. Would you be kind enough to analyze that ?

    I can email/post it as you will.



  13. Reed Robison says:

    Sure… I actually wrote a little tool for analyzing dumpmem logs that I intend to post one of these days. =)  Just email me…reedr at microsoft dot com.

  14. Vijay_Visana says:

    Thanks for eyeopening article!!

    To test my device I have created an application called memmonster.exe

    When I ran dumpmem I got following probably lowest dll position

    shell32.exe base address: 0E000000


    wlmhssearchbarcode.dll 00F20000     C000 RO, S, C, RAM from ROM

      wcplugin.dll 00F80000     6000 RO, S, C, RAM from ROM

    but when I loadded one test dll (mytestdll.dll) from my application it was loaded at much higher position

    at 7F790000

    MemMonsterTest.exe base address: 24000000


        ossvcs.dll 02FCD000    44000 RO, S, XIP

      oleaut32.dll 03011000    2F000 RO, H, S, XIP

         ole32.dll 03040000    2C000 RO, H, S, XIP

      commctrl.dll 031EE000    6A000 RO, H, S, XIP

        shutil.dll 033AD000     7000 RO, H, S, XIP

      aygshell.dll 03752000    57000 RO, H, S, XIP

      htmlview.dll 03C3D000     6000 RO, H, S, XIP

       coredll.dll 03F4A000    97000 RO, H, S, XIP

        xt9ime.dll 78180000    6A000 A

     mytestdll.dll 7F790000     6000 A

    commctrl.dll.0409.mui 7FF80000     2000 RO, S, XIP

    coredll.dll.0409.mui 7FFE0000    15000 RO, S, XIP

  15. Patrick says:

    Great articles, thank you so much. Unfortunately the DumpMem.exe is no longer available anywhere. Do you have a copy laying around somewhere? Or do you know of any viable alternatives? I tried Motorola eMScript, but it didn't dump those DLLs I was interested in (those causing the DLL crunch).

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