I'm wondering if you ever figured out what was going on here; and if (and how) you resolved it. Did you have many objects reaching gen2 that were not "for the duration of the application" objects, which eventually went away, causing lots of (expensive) gen2 collections?
At 04:12 AM 1/27/2004, Bert Roos wrote >Hi, > >We're having a strange problem that seems to be related to garbage collection. We're >performing load testing through a load generator tool (LoadRunner). At a certain load >level, the response times show strange and heavy fluctuations. Request handling times >go up by a factor 10 over an extended period of time (several minutes, up to 10 >minutes). Analysis of performance counters gave some interesting results: > >* Context switches go up heavily >* Contention rate/sec (.NET CLR LocksAndThreads) goes up heavily >* Time spent in GC (.NET CLR Memory) goes up heavily >* Gen 0 heap size (.NET CLR Memory) falls back from fluctuating around 5MB to a >flat 1MB >* Gen 1 heap size (.NET CLR Memory) falls back from fluctuating around 850KB to >nearly nearly flat 350KB >* Gen 2 heap size (.NET CLR Memory) keeps fluctuating around 29MB. At one >point, it goes up a few MBs in but this might be unrelated. > >The test is running on a 4 processor server with 1.5GB RAM. > >According to the documentation, the heap size for generation 0 is the upper limit on >memory allocated in generation 0. When this limit is reached, garbage collection on >generation 0 occurs. The garbage collector tunes this value. > >Based on this and the numbers above, I come to the conclusion that the context >switches are caused by garbage collection. For some to me unknown reason, the GC >lowers its generation 0 heap size to a bare minimum. Due to that, it must collect >like crazy, practically killing the system. > >Can someone explain why this happens and how we can prevent it? > >Thanks, Bert Roos J. Merrill / Analytical Software Corp =================================== This list is hosted by DevelopMentor� http://www.develop.com Some .NET courses you may be interested in: NEW! Guerrilla ASP.NET, 17 May 2004, in Los Angeles http://www.develop.com/courses/gaspdotnetls View archives and manage your subscription(s) at http://discuss.develop.com
