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Async Sockets, pinned objects and .NET 2.0application that use asynchronous sockets intensively (with more than 300 active connections on average) With .NET 1.1 I had problems because the buffers used in the BeginReceive and BeginSend calls were pinned and prevented the heap to be compacted by the GC. I managed to solve this problem by allocating the buffers at the application start up using a buffer pool. Now, in the same application, compiled with .NET 2.0 the heap is heavily fragmented. I can see with perfmon that the pinned objects counter is about 4 times the number of pending asynchronous calls (it was exactly equal in .Net 1.1), so it seems that .NET 2.0 pins 4 objects for each asynchronous socket call instead of pinning only the buffer. This make senseless the approach of using a buffer pool (I get the same memory footprint in .NET 2.0 using the buffer pool or not using it). And the improvements done in .NET 2.0 in managing pinned objects are not good enough, so the situation became worse. Am I wrong with this conclusion? If not, Is there any workaround for this? or a way I can do that the asynchronous socket calls pins only the sending/receiving buffer? What other objects is .NET 2.0 pinning in the asyn socket calls? Thanks The behavior you're seeing doesn't match the behavior that I've seen. We've
done quite a bit of stress testing on an .Net 2.0 Async Sockets application (and on .Net 1.1). We've got the same basic approach you use - a buffer pool pre-allocated to aviod heap fragmentation, heave use of async sockets, and lots of data in and out. We're doing a much higher socket count that you are - we consistantly have 10k+ sockets, and during stress testing many, many more than that. One of my co-workers wrote up the basic memory management issues in detail at: http://www.coversant.net/dotnetnuke/Coversant/Blogs/tabid/88/EntryID/9/Default.aspx (although if you're already allocating buffers and such, you won't get much out of it). Given the overall very positive experience we've had with sockets since moving to .Net 2.0, I would take a look through your application for other stuff. Use one of the memory bebugging tools to try to figure out what's pinned - perhaps it's not your sockets buffers? Show quote "LPJJ" <L***@discussions.microsoft.com> wrote in message news:9743DD2F-3996-43F6-AA71-587EDCC82C68@microsoft.com... > Hi, I am migrating an application from .NET 1.1 to .NET 2.0. It is a > network > application that use asynchronous sockets intensively (with more than 300 > active connections on average) > > With .NET 1.1 I had problems because the buffers used in the BeginReceive > and BeginSend calls were pinned and prevented the heap to be compacted by > the > GC. I managed to solve this problem by allocating the buffers at the > application start up using a buffer pool. > > Now, in the same application, compiled with .NET 2.0 the heap is heavily > fragmented. I can see with perfmon that the pinned objects counter is > about 4 > times the number of pending asynchronous calls (it was exactly equal in > .Net > 1.1), so it seems that .NET 2.0 pins 4 objects for each asynchronous > socket > call instead of pinning only the buffer. > > This make senseless the approach of using a buffer pool (I get the same > memory footprint in .NET 2.0 using the buffer pool or not using it). And > the > improvements done in .NET 2.0 in managing pinned objects are not good > enough, > so the situation became worse. > > Am I wrong with this conclusion? If not, Is there any workaround for this? > or a way I can do that the asynchronous socket calls pins only the > sending/receiving buffer? What other objects is .NET 2.0 pinning in the > asyn > socket calls? > > Thanks > Thanks for your response and thanks the article. The only one recomendation I
am not doing is to use a buffer pool also for the sending packets, but I was not using it with .NET 1.1 and it worked well... I do not know how to identify the pinned ojects, can someone help me on this? I can see that with .NET 2.0 I have 4 more times pinned objects than the same application had with .NET 1.1, and the pinned objects seems to be clearly related to the number of active connections since they use to be 4 times the number of active connections. Can someone canfirm this? Thanks  |
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