LV memory leak - How to use windows API SetProcessWorkingSetSize (from Kernel32.dll)

Question

Hi fellow LV'ers
Okay - this is a bit tricky, but i'll try and explain the problem, then ask for the solution, because it may be that someone knows a better way to deal with this.. might get a bit long, sorry - if a solution comes up this will enable all of us to make more memory efficient LV code so please read on..
Here is the deal:
When building even a very simple LV executable, looking at the windows task manager will yield a rather large amount of memory allocated for such a small program - and the only way to free this up is by physically clicking the windows minimize button, then suddenly the amount drops to only a few MB and upon maximizing the window again the memory consumption will increase somewhat again, but for a simple VI build to an exe this move may change the consumption from +70MB to less than 15 MB.. This is irregardless of the code you put in the VI, so no coding example in this post as it is how LV works - you can even test it with the development environment - look at the task mgr and check LabVIEW's memory consumption, minimze ALL open NI windows incl project explorer etc, and you will see a significant decrease in memory usage even after maximizing again.. This has annoyed me since day one, but since RAM is a near zero cost these days it is not something I stay awake at night to think about.. However - I have moved into the "publish to web" tools now, wanting to do a remote monitoring part for my application for my customers to experience increased usability from the software i sell them..
All is well, publishing is really easy (i use the monitor function, NOT the embeded, as customers need not have Labview RunTimeEngine installed, because they might look at it from a non RTE supported platform such as a mobilephone web browser)
Everything is working fine also for the build application. However - I have noticed that once users start to remote monitor the running application - memory consumption of the running LV application starts to increase - and it keeps doing so - to such an extend that you can drain the computer complete and run off the cliff with a windows error... This is off course not very productive for me, being specialized in measurement applications that usually runs for a long period of time - I initially thought that I had done some poor programming in the VI used to display on the webpage - but it turns out that I can reproduce this behaviour with a simple boolean on an empty front panel..
NI support has been informed, and they admit there is a problem, but so far solutions from them has been a bit too exotic for my taste, and thus I'm seeking the help of fellow LV programmers...
You see - The method to solve the increasing memory consumption, is the exact same as mentioned above..minimize the application running with the "minimize" button and all memory will be freed, as soon as you maximize the application and users are viewing it remotely, the memory usage raises again, and history repeats... As previously mentioned, minimizing the window via normal LV calls to property nodes does not yield the same result, nor does a request deallocation of a VI(When you profile a project, there are no VI's increasing in memory, it is the LV process it self doing it) 
After many many hours googling I stumbled upon this:
http://support.microsoft.com/?kbid=293215
I believe trimming the process with SetProcessWorkingSetSize would solve this problem, and now I would really like to be able to do this in my program, so that users are not forced to minimize the program every X hour depending on their system size...
However - I have absolutely NO experience in calling windows API from LV, i need someone with that knowledge to provide an example of how to call this.. I've looked at examples on how to do calls to windows API - there is an example in this forum with some llb's in it, and I have gained a fair understanding of how parameters are passed between the calls, but none of those include the "hProcess" handle that is apparently needed for this specific winAPI call to work - Anyone in this forum with the knowledge on how to obtain this handle from a VI, if at all possible, and could provide an example VI for me to use - or even better , someone with the knowledge of how to do this within LV it self??
Your help is much appreciated
Best Regards
Jacob
LV8.6.1 patch something
Win XP 
Solved!
Go to Solution.

Answer 1

Hi Enrico
Finally I can give something to the community that has given me so much  :-)
The "official" statement is that "yes we know it is a problem".. Not sure what that will do to the future.. 
I have the problem on 8.6.1 as well  - and in fact it is a general LV problem, that I first time reported to NI with LV8.2 as I was pissed by the fact that even the smallest exe file would consume + 50MB of memory until you manually minimized the window. Well - thanks to the feedback from Cosmin I seem to have solved the problem.
I most warn that having started to "empty process" once in a while has led to occasional program crashes in the lethal "app.exe performed an illegal action and is closed" windows dialog - however what I did was to move the webserver to a seperate exe file and then communicate the data that I want to use via datasocket in a cluster.. It works like a charm and I simply stall the single thread that the webserver is running when ever the empty process is called and I have not seen a crash since then.. (the initial implementation was done in the main app with 4 parallel loops running, and I guess that was a disaster waiting to happen)
Either way - what I have done is made a VI that at a user defined interval calls the empty process, simply by getting the .exe name from the task manager of the calling program - it is simple and very effective. I call it every 5 minutes - needless to say that flushing too often will most likely kill performance of the system. I have not noticed problems with VM - are you sure you are not storing large arrays or moving around copies of data not used frequently?
For future reference to this forum, it is attached here including the .dll required to call - it is a LV8.6.1 file as I have not had the time to yet again test every single function of my program for new problems that could occur with upgrading to LV2009 
I hope this solves your problem..
best regards
Jacob
www.10EaZy.com 
Attachments:
EmptyProcess.zip ‏32 KB