Memory Leakage in dlls called through JNI

I have some dll that are called through a JNI code that have a memory leakage. I need to find how much is that.
Do we have some functions for that to find it in the code.Is that possible without making changes in the JNI code.
I checked but all suggest a memory leakage tool.But i want to do that writing a code in Java.I have checked for the Runtime class but it only finds the JVM related memory usage and not the dll one.

amol28 wrote:
But i want to do that writing a code in Java.Not possible. JNI/C/C++ is not java. So you can't use java to verify it.
I checked but all suggest a memory leakage toolEither that or you manually inspect and/or test the code yourself (in C/C++).

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Hello,
In Firefox 23, as part of an effort to simplify the Firefox options set and protect users from unintentially damaging their Firefox, the option to disable JavaScript was removed from the Firefox Options window.
However, the option to disable JavaScript was not removed from Firefox entirely. You can still access it from about:config or by installing an add-on.
'''about:config'''
# In the address bar, type "about:config" (with no quotes), and press Enter.
# Click "I'll be careful, I promise"
# In the search bar, search for "javascript.enabled" (with no quotes).
# Right click the result named "javascript.enabled" and click "Toggle". JavaScript is now disabled.
To Re-enable JavaScript, repeat these steps.
'''Add-ons'''
You can alternatively install an add-on that lets you disable JavaScript, such as
*[https://addons.mozilla.org/firefox/addon/noscript/ No-Script] (to disable JavaScript on a per page basis, as required)
*[https://addons.mozilla.org/firefox/addon/quickjava/ QuickJava] (to easily disable and enable JavaScript, automatic loading of images, and other content)
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Getting HeapDump on out of memory error when executing method through JNI

I have a C++ code that executes a method inside the jvm through the JNI.
I have a memory leak in my java code that results an out of memory error, this exception is caught in my C++ code and as a result the heap dump is not created on the disk.
I am running the jvm with
-XX:+HeapDumpOnOutOfMemoryError
-XX:HeapDumpPath=C:\x.hprof
Any suggestions?
Thanks

I'll rephrase it then.
I have a java class named PbsExecuter and one static method in it ExecuteCommand.
I am calling this method through JNI (using CallStaticObjectMethod). sometimes this method causes the jvm to throw OutOfMemoryError and I would like to get a heap dump on the disk when this happens in order to locate my memory leak.
I've started the jvm with JNI_CreateJavaVM and I've put two options inside the JavaVMInitArgs that is used to create the Jvm. -XX:+HeapDumpOnOutOfMemoryError and -XX:HeapDumpPath=C:\x.hprof
which supposed to create a heap dump on the disk when OutOfMemoryError occurs.
Normally if I would execute normal java code, when this exception would occur and I wouldn't catch it the Jvm would crash and the heap dump would be created on the disk.
Since I need to handle errors in my C++ code I am use ExceptionOccured() and extracts the exception message from the exception it self and write it.
For some reason when I execute this method through JNI it doesn't create the dump.

Java.lang.Class- getFields() results in JVM crash when called through JNI

From a C++ application, I use Invocation APIs to create a JVM and call some Java methods using JNI
I get a crash in jvm.dll with EXCEPTION_ACCESS_VIOLATION
when I try to call "getFields" method of java.lang.Class in order to get the Fields of the java class
This method call, should return a java/lang/reflect/Fields[] on success
I am able to get the method ID of this method by using pEnv->GetMethodID(..)
However, when I call this method using CallObjectMethod(..), HotSpt JVM crashes with access violation with the dump given below.
Any clues on how to debug and find the problem?
Or has anyone tried getting the fields of a Java class from C++ by calling reflection APIs uing JNI?
Thanks in advance!
Sample code
jclass testerClass = pEnv->FindClass("com/test/Tester");
jmethodID cid = pEnv->GetMethodID(testerClass,"<init>","()V");
if(NULL == cid)
pEnv->ExceptionDescribe();
jobject testerObject = pEnv->NewObjectV(testerClass, mid);
jmethodID mid = pEnv->GetMethodID(testerClass, "getClass",
                         "()Ljava/lang/Class;");
jobject clsObj = (jobject)pEnv->CallObjectMethod(testerObject, mid);
pEnv->ExceptionDescribe();
jclass      jCls = pEnv->GetObjectClass(clsObj);
jmethodID midGetFields = pEnv->GetMethodID(jCls, "getFields",
                                        "()[Ljava/lang/reflect/Field;");
jobjectArray jobjArray = (jobjectArray)pEnv->CallObjectMethod(testerObject, midGetFields);
pEnv->ExceptionDescribe();
Crash dump
Unexpected Signal : EXCEPTION_ACCESS_VIOLATION (0xc0000005) occurred at PC=0x809E69F
Function=JVM_FindSignal+0x11505
Library=D:\Java\j2re1.4.2_03\bin\client\jvm.dll
Current Java thread:
     at java.lang.Class.privateGetDeclaredFields(Unknown Source)
     at java.lang.Class.privateGetPublicFields(Unknown Source)
     at java.lang.Class.getFields(Unknown Source)
Dynamic libraries:
0x00400000 - 0x00419000      E:\SC\SC12.1\SCApplications\SNMP\Bin\JNITester.exe
0x77F50000 - 0x77FF7000      C:\WINDOWS\System32\ntdll.dll
0x77E60000 - 0x77F46000      C:\WINDOWS\system32\kernel32.dll
0x10000000 - 0x10023000      E:\SC\SC12.1\SCApplications\SNMP\Bin\JniUtils.dll
0x00320000 - 0x00332000      E:\SnmpIpmNativeTestDriver\MTFStubHelper.dll
0x00340000 - 0x0035B000      E:\SnmpIpmNativeTestDriver\MTFXMLFileAPI.dll
0x12000000 - 0x122B1000      e:\sc\sc12.1\bin\xerces-c_2_2_0D.dll
0x77DD0000 - 0x77E5D000      C:\WINDOWS\system32\ADVAPI32.dll
0x78000000 - 0x78086000      C:\WINDOWS\system32\RPCRT4.dll
0x10200000 - 0x1026C000      e:\sc\sc12.1\bin\MSVCRTD.dll
0x102A0000 - 0x102B7000      e:\sc\sc12.1\bin\MSVCIRTD.dll
0x5F800000 - 0x5F8E9000      e:\sc\sc12.1\bin\MFC42uD.DLL
0x77C70000 - 0x77CB0000      C:\WINDOWS\system32\GDI32.dll
0x77D40000 - 0x77DCC000      C:\WINDOWS\system32\USER32.dll
0x5F700000 - 0x5F746000      e:\sc\sc12.1\bin\MFCD42uD.DLL
0x5F500000 - 0x5F5C6000      e:\sc\sc12.1\bin\MFCO42uD.DLL
0x10480000 - 0x104FE000      e:\sc\sc12.1\bin\MSVCP60D.dll
0x15020000 - 0x15042000      e:\sc\sc12.1\bin\SCTraceLib.dll
0x6D510000 - 0x6D58D000      C:\WINDOWS\System32\dbghelp.dll
0x77C10000 - 0x77C63000      C:\WINDOWS\system32\msvcrt.dll
0x77C00000 - 0x77C07000      C:\WINDOWS\system32\VERSION.dll
0x00360000 - 0x0037D000      e:\sc\sc12.1\bin\SCFileManager.dll
0x76BF0000 - 0x76BFB000      C:\WINDOWS\System32\PSAPI.DLL
0x00420000 - 0x00580000      e:\sc\sc12.1\bin\BctCoreCL.dll
0x5D920000 - 0x5D929000      C:\WINDOWS\System32\RPCNS4.dll
0x71B20000 - 0x71B31000      C:\WINDOWS\system32\MPR.dll
0x71C20000 - 0x71C6E000      C:\WINDOWS\System32\NETAPI32.dll
0x71AB0000 - 0x71AC5000      C:\WINDOWS\System32\WS2_32.dll
0x71AA0000 - 0x71AA8000      C:\WINDOWS\System32\WS2HELP.dll
0x15000000 - 0x15012000      e:\sc\sc12.1\bin\CTEventLog.dll
0x773D0000 - 0x77BC2000      C:\WINDOWS\system32\SHELL32.dll
0x70A70000 - 0x70AD4000      C:\WINDOWS\system32\SHLWAPI.dll
0x771B0000 - 0x772D1000      C:\WINDOWS\system32\ole32.dll
0x77120000 - 0x771AB000      C:\WINDOWS\system32\OLEAUT32.dll
0x1F7A0000 - 0x1F7D6000      C:\WINDOWS\System32\ODBC32.dll
0x77340000 - 0x773CB000      C:\WINDOWS\system32\COMCTL32.dll
0x763B0000 - 0x763F5000      C:\WINDOWS\system32\comdlg32.dll
0x08000000 - 0x08138000      D:\Java\j2re1.4.2_03\bin\client\jvm.dll
0x76B40000 - 0x76B6C000      C:\WINDOWS\System32\WINMM.dll
0x5FD00000 - 0x5FD0D000      C:\WINDOWS\System32\MFC42LOC.DLL
0x71950000 - 0x71A34000      C:\WINDOWS\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.10.0_x-ww_f7fb5805\comctl32.dll
0x1F840000 - 0x1F857000      C:\WINDOWS\System32\odbcint.dll
0x5DAC0000 - 0x5DAC7000      C:\WINDOWS\System32\rdpsnd.dll
0x00FE0000 - 0x00FE7000      D:\Java\j2re1.4.2_03\bin\hpi.dll
0x01000000 - 0x0100E000      D:\Java\j2re1.4.2_03\bin\verify.dll
0x01010000 - 0x01029000      D:\Java\j2re1.4.2_03\bin\java.dll
0x01030000 - 0x0103D000      D:\Java\j2re1.4.2_03\bin\zip.dll
0x76C90000 - 0x76CB2000      C:\WINDOWS\system32\imagehlp.dll
Heap at VM Abort:
Heap
def new generation total 576K, used 132K [0x15050000, 0x150f0000, 0x15530000)
eden space 512K, 25% used [0x15050000, 0x15071250, 0x150d0000)
from space 64K, 0% used [0x150d0000, 0x150d0000, 0x150e0000)
to space 64K, 0% used [0x150e0000, 0x150e0000, 0x150f0000)
tenured generation total 1408K, used 0K [0x15530000, 0x15690000, 0x19050000)
the space 1408K, 0% used [0x15530000, 0x15530000, 0x15530200, 0x15690000)
compacting perm gen total 4096K, used 964K [0x19050000, 0x19450000, 0x1d050000)
the space 4096K, 23% used [0x19050000, 0x191410e0, 0x19141200, 0x19450000)
Local Time = Wed Aug 25 21:06:44 2004
Elapsed Time = 0
# HotSpot Virtual Machine Error : EXCEPTION_ACCESS_VIOLATION
# Error ID : 4F530E43505002EF
# Please report this error at
# http://java.sun.com/cgi-bin/bugreport.cgi
# Java VM: Java HotSpot(TM) Client VM (1.4.2_03-b02 mixed mode)

You are right, I tried getting the java.lang.Class reference for the com.test.Tester by calling getClass() on com.test.Tester
And using this jclass reference for java.lang.Class, I tried getting the method ID of getFields and eventually the Field[]
Thanks for the help
I have some more questions.
Assumption - Using JNI, I got the fields array of com.test.Tester and I am iterating through the fields
1.Assuming that the Tester class had an Integer field say m_nIntVal, then once I get the jobject equivalent of this Field in C++.
Now I need to get the type of the field (I call the method java.lang.reflect.getType() from JNI)
This gives me a jclass reference to it's type i.e java.lang.Integer
2.I need to get the name of this type i.e I want to get the name of the type in a string as "java.lang.Integer"
For this, on the jclass reference of java.lang.Integer got in Step 1, I call getClass() from JNI (to get the java.lang.Class) and then getName()
Now, for calling getClass(), I need a temporary object reference corresponding to the jclass of java.lang.Integer, The problem is that Integer does not have a default constructor, so my call to create the jobject fails.
But, since I do not know that I am constructing an Integer (remember that is what I am trying to find out - getType), I cant pass any values to constructor
Now, how do I go about creating a jobject of Integer, without knowing that I am constructing that, as this does not have a default constructor without parameters
Also, I tried using AllocObject to get the jobject and then tried to get the method ID of getClass(). Even this failed
3. If the com.test.Tester class had a primitive "int" field, say m_nPrimitiveInt
for which java provides a Class representation, I am able to get the jclass reference to the type of m_nPrimitiveInt
Now, how do I get the name of the type as "int" in a string?
Forllowing a similar procedure like in Step 2 fails when I try to pass the jclass reference to the type of m_nPrimitiveInt to the GetMethodID
with the error FATAL ERROR in native method: JNI received a class argument that is not a class
Can you tell me what is the way out?
Thanks in advance,
Also, can I mail you with some doubts that I have? If its ok, please contact me at [email protected]

Creating a window through a DLL called through CLFN

Hi, sorry if this is a relatively simple problem but I've been unable to find proper results after a couple hours or so of searching.
My group is interacting wtih a DLL that requires a window to draw to. We tried drawing directly to a LabVIEW window (using the FindWindow function through the Windows API), however while that worked we were unable to save the drawn image (the Front panel-> export image invoke node wouldn't save the drawn image).
So, what we did was write some C code and make a wrapper DLL that creates a window to draw to through the CreateWindow function, which we would then export to our main vi (less than ideal, but that's another problem). However, when we call up this wrapper DLL via the CLFN, it won't create the window. Windows doesn't throw an error, it just won't instantiate the window at all and the function returns an error that the window was never created. The reason I'm posting this problem here instead of a general C++ forum is because we've tested out this wrapper DLL via a test project that imports the DLL and it works fine.
This is how I'm setting up the window. I pass the LabVIEW Window found via the FindWindow function in as hInst (sorry for the formatting, I tried the HTML <code> tag and the board doesn't seem to accept it):
int initializeWindow(HINSTANCE hInst)
    // Initialize global strings
    LoadString(hInst, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
    LoadString(hInst, IDC_WINDOW_CLASS, szWindowClass, MAX_LOADSTRING);
    MyRegisterClass(hInst);
    // Perform application initialization:
    if (!InitInstance (hInst, 1))
        return 0;
    return 1;
ATOM MyRegisterClass(HINSTANCE hInst)
    WNDCLASSEX wcex;
    wcex.cbSize = sizeof(WNDCLASSEX);
    wcex.style            = CS_HREDRAW | CS_VREDRAW | CS_BYTEALIGNCLIENT;
    wcex.lpfnWndProc    = WndProc;
    wcex.cbClsExtra        = 0;
    wcex.cbWndExtra        = 0;
    wcex.hInstance        = hInst;
    wcex.hIcon            = LoadIcon(hInst, MAKEINTRESOURCE(IDI_UVIEW));
    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground    = (HBRUSH)(COLOR_WINDOW+1);
    wcex.lpszMenuName    = MAKEINTRESOURCE(IDC_UVIEW);
    wcex.lpszClassName    = szWindowClass;
    wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
    return RegisterClassEx(&wcex);
BOOL InitInstance(HINSTANCE hInst, int nCmdShow)
   hwnd = CreateWindow(szWindowClass, szTitle, WS_VISIBLE | WS_DLGFRAME | SS_BLACKRECT,
    0, 0, X_WINDOW_SIZE, Y_WINDOW_SIZE, NULL, NULL, hInst, NULL);
   if (hInst == NULL)
        MessageBox(hwnd, TEXT("Problem making instance"), TEXT("ERROR"),0);
        return FALSE;
   if (!hwnd)
    MessageBox(hwnd,TEXT("Problem making window"),TEXT("ERROR"),0);
    return FALSE;
   ShowWindow(hwnd, nCmdShow);
   UpdateWindow(hwnd);
   return TRUE;
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
// Standard WndProc implementation.. probably not worth posting all the code unless necessary
Does anyone see an obvious problem? Or something I should try?
Thanks in advance!
Message Edited by wgerard on 05-16-2010 12:18 AM

I can be short about that. A Windows HINSTANCE is NOT a HWND by a long stretch. The first is a module handle and the second is ... well yes a window!
FindWindow() returns a HWND and you can use that as parent handle for another window, but you can not use it as HINSTANCE ever.
To get at the HINSTANCE for registering new window classes you will need to extract that somehow from the HWND, probably by something like GetWindowLongPtr(.., GWLP_HINSTANCE, ..) or something similar.
But you won't be able to retrieve your own resources from that instance, because it is the instance for the LabVIEW executable, not your DLL.
Message Edited by rolfk on 05-16-2010 10:31 AM
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

JSP Call C Library through JNI ?

Hi experts :
I has a jsp file which create a bean to call native c method.
It still works fine after 10 to 14 times' page refresh, then
it throws exception when call a native method.
If I restart the Tomcat it works again ,but shuch situtation repeat again.
Should I notice any issues when access native c library
through JNI in jsp ?
Environment:
SPARC 64 Solaris 7
Tomcat 4.0.4
JDK 1.3.1-04

hi CTSteven
Did you find a solution for this JNI-Problem ? I think i have the same problem as you. Would be great to here from you.
Thank you.
Bye
Lukas

Is JMF use hardware accelerated through JNI possible?

Dear all:
I try to use JMF decode MPEG-2 data, through VeXP which wrote in C.
So I think we can call C library through JNI pass encoded MPEG-2 data to VeXP, use hardware decode encoded MPEG-2 data to YUV-format raw data then return it to JAVA.
but JNI seem can't pass media raw data by call by reference...
It should cause a lot of memory copy.
How about it's feasibility?
Have anyone give me some suggestion?
Regards,
white

There's a few ways to do it, but I'd use a style sheet. So:
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2. Create a style sheet (text file) in your project folder named "styles.css", and define a class:
.force-webkit-acceleration {
-webkit-transform: translate3d(0,0,0);
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Be sure that the style sheet file ends up in your "publish/web" folder too.

Failure: "gnrclist.cpp" after a DLL call

Forum:
Since adding dll calls in a VI, LabVIEW is frequently crashing, both during VI execution and after exiting the application.
Generally, what issues need to be considered when making successful dll calls (using the "call library function").
Jordan

Hi Jordan,
It sounds like this issue is due to the fact that you are not allocating memory for the dll in advance. This is the most common mistake when implementing a dll in LabVIEW.
For instance, if your dll is going to output an array of 100 double-precision numbers, then you need to allocate this place in memory by passing the dll a dummy array of 100 double-precision numbers that it can operate on. Also be careful not to expand the size of the array. LabVIEW doesn't support dynamic memory allocation within a dll in most circumstances. If you don't allocate a place in memory in advance, LabVIEW may crash when you exit the program and LabVIEW tries to deallocate memory.
A really good example of allocating various types of data for use in a dll is available from the Example Finder (Help >> Find Examples from LabVIEW). Click the Search tab and search for the term DLL. The Example is called Call DLLs. It contains c code that corresponds to various dll functions that operate on various data types, and it shows you how to call these dll functions properly from LabVIEW. For a more comprehensize overview of the process, refer to the document Using External Code in LabVIEW, available here, or browse through these Developer Zone examples and applications notes.
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National Instruments

Memory leakage issue in Oracle-DOTNET environment

Hi,
One of my customer is facing a issue of memory leakage issue with their ASP.NET application. Following are the environment details
1. ASP.NET 3.5 application (Uses some Infragistics controls for grids)
2. SSRS for reporting
3. Oracle Server as database (details given below)
The memory leakage occurs while running load testing in his test environment.
The memory is consumed (in tune of 1.2 GB) and then performance is hit.
The memory dump is analyzed and we found Oracle client eating up a lot of memory which is not released.
We tried to use 11g driver also but without any improvements.
Environment Details :
1. Oracle server version –
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE 10.2.0.1.0 Production
TNS for 32-bit Windows: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 – Production
2. Client version
We are using following oracle client version SQL*Plus: Release 10.2.0.1.0 – Production
(For performance purpose we have used following client version. SQL*Plus: Release 11.1.0.7.0 – Production)
3. ODP.NET version
Version of Oracle.DataAccess.dll is 2.111.7.10
It will be great if any body can help on this issue and guide us on the right track.
Thanks in advance.
Thanks & Regards,
Anoop

Please test it with release version as there may be a lot of things which are fixed after beta.
Also please note down the statement cache size your application was using earlier. Starting from 2.111.7.10/2.111.7.20, the statement cache size is automatically tuned by default. This feature is called self tuning. You may disable self tuning and specify your own statement cache size as usual. To know more about self tuning, please consult ODP.NET Developer's Guide.
I would suggest that you first upgrade to the release version 2.111.7.20. If that does not solve the problem, you may either
- specify MaxStatementCacheSize
or
- disable self tuning and provide your own statement cache size

How do I create a fault-tolerant DLL call from LV?

I've created an .exe from a VI that calls a DLL, when that DLL crashes,
it crashes the whole application. This DLL is too complicated to
completely debug and it, in turn calls DLLs I have no control
over. It crashes approximately once every 100,000 iterations.
How do I make a DLL call fault-tolerent?
Attachments:
crash.gif ‏19 KB

I might not have been very clear in my answer - this isn't a feature that CAN be added to LabVIEW...the DLL threw an unhandled exception across a DLL interface - which pretty much means a system exception (code shouldn't be throwing language exceptions across DLL boundaries as they are language specific). This means that something went very wrong with the code and there is a good chance that the process space has been corrupted. And from my own debugging experience, if it's only crashing 1 time out of 100,000, that doesn't mean it isn't corrupting memory or otherwise causing problems...it was just the time it was caught.
Considering this, the Call Library Node already is fault tolerant - we catch the exception and report it to the user. You have a valid position that we should simply return this as an error. It's also a valid position that it would be a road paved with good intentions. All you need to do is remember what life was like in Windows 3.1 - where one process could silently corrupt another - to realize the amount of untraceable errors that could occur. Yes, the error out value should be handled by the user, but when an application of 100's or 1000's of VIs crashes seemingly at random because someone didn't, you can see the problem.
I will say I like the idea of a separate memory space. It is unfortunate that Windows only offers that through creating a separate process, but it is a neat idea. I worked in the VXI/VME world for a while, which does have multiple address spaces.
BTW - using signal handlers to catch exceptions is unfortunately not a 100% solution...signals are a partial port of a Unix concept in Windows. You would be best to use SEH around the call (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/key_s-z_4.asp). If the DLL is already a C++ DLL, then you can use the global catch of C++ instead
int err = 0;
try {
} catch(...) {
err = -1;
Again, you still are at risk of a corrupted process, but this allows you to avoid our handling of it.
Having spent years writing and (god help me) debugging device drivers, I love this topic. If you want to talk more about it and various options, feel free to shoot me an email at [email protected].
Brian Tyler
http://detritus.blogs.com/lycangeek

Stand alone weblogic keeps running out of memory ! Cause of Memory Leakage?

Hi all,
I have a machine with 16gb ram and 500gb hard disk with linux os. I have installed weblogic server in it with an adf application deployed on it. So now the problem every two weeks the machine keeps running out of memory . Could it be because of connection leakage ?
There are only a couple of people accessing the application time and again.
When i checked for the data source connection count in weblogic server under data sources , it mostly shows around 10 - 20 connections.
What are various reasons for leakage of connection in ADF application ?
I have not made any explicit jdbc calls in our application .
There is a couple of PL/SQL calls to an external api(this is done in the application module) through db links and rest all is just plain accessing of application modules and view objects .
So what could be the reason if any memory leakage is occuring ?
My application module configuration is
<AppModuleConfigBag ApplicationName="model.am.AuthenticationAM">
      <AppModuleConfig jbo.project="model.Model" DeployPlatform="LOCAL" name="AuthenticationAMLocal" ApplicationName="model.am.AuthenticationAM">
         <AM-Pooling jbo.ampool.maxinactiveage="300000" jbo.ampool.initpoolsize="44" jbo.ampool.maxpoolsize="60" jbo.recyclethreshold="40" jbo.ampool.minavailablesize="0" jbo.ampool.monitorsleepinterval="120000"/>
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Sam
Edited by: Sam47 on 19-Oct-2012 01:46

Hi Suspito ,
Thanks for the link ..
Is that the standard configuration for weblogic server?
If at all there are connection leaks in the application in the weblogic server under datasource will it show the count of all the database connection open ?
-Sam

Avoiding data memory duplication in subVI calls

Hi,
I am on a Quest to better understand some of the subtle ways of the LabVIEW memory manager. Overall, I want to (as much as practically possible) eliminate calls to the memory manager while the code is running.
(I mainly do RT code that is expected to run "forever", the more static and "quiet" the memory manager activity is, the faster and simpler it is to prove beyond reasonable doubt that your application does not have memory leaks, and that if will not run into memory fragmentation (out of memory) issues etc. What I like to see as much as possible, are near static "used memory" and "largest contiguous block available" stats over days and weeks of deployed RT code.)
In my first example (attached, "IPE vs non-IPE.png"), I compared IPE buffer allocation (black dots) for doing some of the operations in an IPE structure vs. "the old way". I see fewer dots the old way, and removed the IPE structure.
Next I went from initializing an array of size x to values y to using a constant array (0 values) with an "array add" to get an array with the same values as my first version of the code. ("constant array.png")
The length of the constant array is set to my "worst case" of 25 elements (in example). Since "replace sub-array" does not change the size of the input array even when the sub-array is "too long", this saves me from constantly creating small, variable sized arrays at run-time. (not sure what the run-time cpu/memory hit is if you tried to replace the last 4 elements with a sub-array that is 25 elements long...??)
Once I arrived at this point, I found myself wondering "how exactly the constant array is handled during run-time?". Is it allocated the first time that this sub-vi is called then remains in memory until the main/top VI terminates, or is it unloaded every time the SubVI finishes execution? (I -think- Mac's could unload, while windows and linux/unix it remains in memory until top level closes?) When thinking (and hopefully answering), consider that the the code is compiled to an RTEXE runningg on a cRIO-9014 (vxWorks OS).
In this case, I could make the constant array a control, and place the constant on the diagram of the caller, and pipe the constant all the way up to the top level VI, but this seems cumbersome and I'm not convinced that the compiler would properly reckognize that at the end of a long chain of sub-sub-sub VI's all those "controls" are actually always tied off to a single constant. Another way would perhaps be to initialize a FG with this constant array and always "read it" out from the FG. (using this cool trick on creating large arrays on a shift register with only one copy which avoids the dual copy (one for shift register, one from "initialize array" function)).
This is just one example of many cases where I'm trying to avoid creating memory manager activity by making LabVIEW assign memory space once, then only operate on that data "in-place" as much as possible. In another discussion on "in-place element" structures (here), I got the distinct sense that in-place very rarely adds any advantage as the compiler can pick up on and do "in-place" automatically in pretty much any situation. I find the NI documentation on IPE's lacking in that it doesn't really show good examples of when it works and when it doesn't. In particular, this already great article would vastly benefit from updates showing good/bad use of IPE's.
I've read the following NI links to try and self-help (all links should open in new window/tab):
cool trick on creating large arrays on a shift register with only one copy
somewhat dated but good article on memory optimization
IPE caveats and recommendations
How Can I Optimize the Memory Use in My LabVIEW VI?
Determining When and Where LabVIEW Allocates a New Buffer
I do have the memory profiler tool, but it shows min/max/average allocations, it doesn't really tell me (or I don't know how to read it properly) how many times blocks are allocated or re-allocated.
Thanks, and I hope to build on this thread with other examples and at the end of the thread, hopefully everyone have found one or two neat things that they can use to memory optimize their own applications. Next on my list are probably handling of large strings, lots of array math operations on various input arrays to create a result output array etc.
-Q
QFang
CLD LabVIEW 7.1 to 2013
Attachments:
IPE vs non-IPE.png ‏4 KB
constant array.png ‏3 KB

I sense a hint of frustration on your part, I'm not trying to be dense or difficult, but do realize that this is more towards the "philosophical" side than "practical" side. Code clarity and practicalities are not necessarily the objectives here.
Also, I have greatly appreciated all your time and input on this and the other thread!
The answer to your first question is actually "yes, sort of". I had a RT application that developed a small memory leak (through a bug with the "get volume info.vi' from NI), but to isolate it and prove it out took a very long time because the constant large allocation/deallocations would mask out the leak. (Trace's didn't work out either since it was a very very slow leak and the traces would bomb out before showing anythinng conclusive.) The leak is a few bytes, but in addition to short term memory oscilations and long term (days) cyclical "saw-tooth" ramps in memory usage, made this very hard to see. A more "static" memory landscape would possibly have made this simpler to narrow down and diagnose. or maybe not.
Also, you are missing my point entierely, this is not about "running out of memory" (and the size of 25 in my screen-shot may or may not be what that array (and others) end up being). This is about having things allocated in memory ONCE then not de-allocated or moved, and how/when this is possible to accomplish. Also this is a quest (meaning something I'm undertaking to improve and expand my knowledge, who said it has to be practical).
You may find this document really interesting, its the sort of thing you could end up being forced to code to, albeit, I don't see how 100% compliance with this document would ever be possible in LabVIEW, thats not to say its worthless: JPL Institutional Coding Standard for the C Programming Language (while it is directed at C, they have a lot of valid general points in there.)
Yes, you are right that the IPE would grow the output if the lenght of my replacement array is not the same, and since I can't share the full VI's its a bit of a stretch to expect people to infer from the small screen dummp that the I32 wires on the right guarantee the lengths will match up in the IPE example.
Once, on recomendation of NI support, I actually did use the Request deallocation primitive during the hunt for what was going on in that RT app I was debugging last year. At that particular time, the symptom was constant fragmentation of memory, until the largest contiguous block would be less than a couple of kB and the app would terminate with 60+MB of free memory space.. (AKA memory leak, though we could not yet prove that from diagnostic memory consumption statistics due to the constant dynamic behavior of the program) I later removed them. Also, they would run counter to my goal of "allocate once, re-use forever" that I'm chasing. and again, I'm chasing this more as a way to learn than because all my code MUST run this way.
I'm not sure I see what you mean by "copying data in and out of some temporary array". Previously (before the constant array) at every call to the containing sub-vi, I used to "initialize array" with x elements of value y (where x depends to a large degree on a configuration parameter, and y is determined by the input data array). Since I would call to "initialize" a new array each time the code was called, and the size of the array could change, I looked for a way that I could get rid of the dynamic size, and get rid of dynamically creating the array from scratch each time the sub-vi was called. What I came up with is perhaps not as clear as the old way I did it, but with some comments, I think its clear enough. In the new way, the array is created as a constant, so I would think that would cause less "movement" in memory as it at that point should be preventing the "source" array from (potentially) moving around in memory? Considering the alternative of always re-creating a new array, how is this adding an "extra" copy that creating new ones would not create?
How would you accomplish the task of creating an array of "n" elements, all of value "y" without creating "extra" copies? -auto-indexing using a for loop is certainly a good option, but again, is that sure to reuse the same memory location with each call? Would that not, in a nit-picking way, use more CPU cycles since you are building the array one element at the time instead of just using a primitive array add operation (which I have found to be wicked fast operations) and operate on a constant data structure?
I cannot provide full VI's without further isolation, maybe down the road (once my weekends clear up a bit). Again, I appreciate your attention and your time!
QFang
CLD LabVIEW 7.1 to 2013

Does making objects equal null help the gc handle memory leakage problems

hi all,
does making objects equal null help the gc handle memory leakage problems ?
does that help out the gc to collect unwanted objects ??
and how can I free memory avoid memory leakage problems on devices ??
best regards,
Message was edited by:
happy_life

Comments inlined:
does making objects equal null help the gc handle
memory leakage problems ?To an extent yes. During the mark phase it will be easier for the GC to identify the nullified objects on the heap while doing reference analysis.
does that help out the gc to collect unwanted objects
??Same answer as earlier, Eventhough you nullify the object you cannot eliminate the reference analysis phase of GC which definitelely would take some time.
and how can I free memory avoid memory leakage
problems on devices ??There is nothing like soft/weak reference stuffs that you get in J2SE as far as J2ME is concerned with. Also, user is not allowed to control GC behavior. Even if you use System.gc() call you are never sure when it would trigger the GC thread. Kindly as far as possible do not create new object instances or try to reuse the instantiated objects.
~Mohan

Error Code 1097 Coming in DLL Calling

Hi,
I am getting error code 1097 in DLL calling function. Please find the DLL calling function details for more information.
Function : GetControllerListTest(controller *ptrControllertest,char *max_controller);
Controllertest parameter details:
define NO_OF_CONTROLLER  100
#ifndef CONTROLLER_STRUCT
typedef struct
  CString name;
  char status;
  CString blocked_by;
  char group;
}controller;
Controllertest parameter data type is structure. In LabVIEW, I have configured parameter as a cluster.
name : String control
status : U8 Integer control
blocked_by : String control
group : U8 Integer control
Could you please confirm it, did I configured the datatype in correct way?
I am getting empty array output and Error Code from the DLL 1097. Can you please tell me where I am missing?
Thanks
Sivaramkumar.V
Solved!
Go to Solution.

Call Library Node problems without the VI in question attached AND the complete C prototype of the function provided, AND preferably some documentation about the C function in question can be not diagnosed. These informations are paramount to get the Call Library Node configured properly since there is no way a calling application can retrieve the necessary information from the DLL itself. The DLL interface was never intended to be a self configuring interface and it was designed with the understanding, that the user of such an interface is a fully knowledgeable C programmer knowing both, how to read a header file definition as well as various details about memory buffer handling.
So show us your VI and the C header file, and we can start to help you. Otherwise all we can do is guessing in the way you have done with changing the calling convention randomly. You can of course try to shoot in the shooting range with a blindfold on, but the chances that you not only do not hit the target, but injure some other person instead is very high.
The only reason that the suggestion from Fragger Fox has any merits is the fact that LabVIEW used to have some heuristics that changed the Call Library Node automatically from C calling convention (the LabVIEW default) to Windows calling convention, if it recognized a certain pattern in the exported function name. This heuristic was removed in LabVIEW 2009 because it did prevent the Call Library Node to be able to call functions that were using C calling convention but happened to match the heuristic pattern. So changing a Windows calling convention to C calling convention when the code has "seemed" to work before is NEVER a solution.
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Dll call from java using Jbuilder?

Please?
Does anyone know how I do dll calls from java (jubuilder).
I have tried but did not manage to get it wright???
/ thanks carlos

Research JNI (java native interface)

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