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.NET Forum / .NET Framework / New Users / February 2007Out of control threads
Hello group. I have a vb.net winform app that, in a sub, starts 10 new threads. The sub waits in a loop for these threads to finish before continuing. The end of the sub thread's sub sets a boolean which the main sub's loop checks for. So, the problem is, that after each thread completes it's task, memory is not released and the thread count does not decrease. The main sub loops for x number of items and starts these 10 threads for each item. I've used gc.collect and also Thread.CurrentThread.Abort() at the end of each sub thread's sub. I've disposed of all objects and set them = nothing and also tried GC.GetTotalMemory(True) but nothing seems to want to let me release these threads. Any help would be much appreciated. Thanks, Jeff Instead of setting a boolean, create an array (or collection) of threads and add each thread to it. When you are ready to wait for the threads, do the following (VB.NET): for each th as Thread in myThreads th.Join next th This eliminates the boolean variable, which may be what is keeping the thread in memory. Mike Ober. > Hello group. I have a vb.net winform app that, in a sub, starts 10 > new threads. The sub waits in a loop for these threads to finish [quoted text clipped - 10 lines] > Thanks, > Jeff Hi, I am wondering why you need multithreading in this particular situation. Your main sub waits for threads to finish anyway! Multithreading would make sense only if you started some background task(s) and continued on doing something else. Why not to just execute these thread functions (without creating threads) one aftert another, like this: Sub s() Begin ThreadFunction1() ThreadFunction2() ........ ThreadFunctionN() End This way your sub doesn't have to monitor threads. It just exits after their functions are all finished. > Hello group. I have a vb.net winform app that, in a sub, starts 10 > new threads. The sub waits in a loop for these threads to finish [quoted text clipped - 10 lines] > Thanks, > Jeff > Hi, > [quoted text clipped - 37 lines] > > - Show quoted text - Sometimes you may want to do 10 things in parralel (like visit 10 websites and scrape some info). This is much faster when you use 10 threads, then doing it sequentially, as the bottleneck is latency, not CPU. I have personally used a method described above, and it works great. You may need to retrieve values from different databases, and then perform some calculation using them. You can only start the calculation once you have the 10 values. Hmm, and if you needed to visit 1000 websites (or databases) would you have created a 1000 threads? I am sure the method works great, but I still have doubts whether or not it can give you any gain in performance. There's still a network cable which allows only this much information to pass at any moment. Say, 100 kbits per second. What if you need 100 kbits from each of the 10 websites? They'll not come all in one second because of multithreading. They'll take exactly 10 seconds. And during multithreading doesn't CPU pass a token between threads and run just a portion of a thread funtion and then move on to the next thread? How is it different from running thread functions sequentially? Besides all the extra steps that CPU has to take because of multithreading? > Sometimes you may want to do 10 things in parralel (like visit 10 > websites and scrape some info). This is much faster when you use 10 [quoted text clipped - 5 lines] > perform some calculation using them. You can only start the > calculation once you have the 10 values. In this case, I would use the threadpool and queue up the threads. You get the benefits of the parallel operations but don't saturate your physical resources. Mike. > Hmm, and if you needed to visit 1000 websites (or databases) would you > have created a 1000 threads? [quoted text clipped - 21 lines] >> perform some calculation using them. You can only start the >> calculation once you have the 10 values. FYI, I do need 10 threads, I have 10 things to do each which take about 20 seconds, if I do sequentially, it would take 200 seconds, if I use 10 threads it takes about 60 seconds, it's not 1 to 1 since there are other factors like DB writing and such... I'll try the pool.. Thanks. Forgot to mention, I had to dispose of everything in any call made by the thread before I could (and had to seemingly) abort the thread at the end of the procedure. I'd crash after 99+ threads and >100 mb of ram usage. Once I properly disposed of my objects (especially a memory stream. (oops)) it stayed at 25 or so threads and 60 mb (which is reasonable for what I'm doing). Thanks again. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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