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garbage collection for hastable.I am writing a class to cache xml and dataset objects that would be required frequently by my application. I also have a time to check the last access of the obect... If the object is not used for some time I would like to remove it from the cashe to free memmory. I am using hastable to store these objects. What I observe is that even if I remove the object from the hastable the memmory is not freed even if I wait a long time (more than 10 mins) to for the Garbage collection cycle to happen. To make sure there was an issue with the garbage collection I wrote a test application. I declared a class variable for Hashtable in one function I am filling the hastable like below for(int i = 0 ; i < 10000; i++) { HTT.Add(Guid.NewGuid().ToString(),new string('d',40000)); } In another function I am calling HTT.Clear() to delete the items during this time I am observing the memmory useage in the taskmanager. The memmory useage rises as expected in the first function call but does not come down after the second function is called. I waited enough for the GC cycle more thant 10 mins... after the HTT.Clear function call if I call CG.Colloect(); then memmory was coming down. I did not want to do that in my app. please suggest. Thanks in advance, Praveen Don't worry about the Garbage Collector. It will run when it needs to. If
you are really trying to reduce your application memory footprint, you need to call the working set size APIs directly. Mike Ober. Show quote "Praveen" <praveen@newsgroup.nospam> wrote in message news:%23wsWVtuXGHA.196@TK2MSFTNGP04.phx.gbl... > > Hello all, > > I am writing a class to cache xml and dataset objects that would be required > frequently by my application. I also have a time to check the last access of > the obect... If the object is not used for some time I would like to remove > it from the cashe to free memmory. I am using hastable to store these > objects. > > What I observe is that even if I remove the object from the hastable the > memmory is not freed even if I wait a long time (more than 10 mins) to for > the Garbage collection cycle to happen. > > To make sure there was an issue with the garbage collection I wrote a test > application. > > I declared a class variable for Hashtable > in one function I am filling the hastable like below > > for(int i = 0 ; i < 10000; i++) > { > HTT.Add(Guid.NewGuid().ToString(),new string('d',40000)); > } > > In another function I am calling HTT.Clear() to delete the items > > during this time I am observing the memmory useage in the taskmanager. The > memmory useage rises as expected in the first function call but does not > come down after the second function is called. > > I waited enough for the GC cycle more thant 10 mins... after the HTT.Clear > function call if I call CG.Colloect(); then memmory was coming down. I did > not want to do that in my app. > > please suggest. > > Thanks in advance, > Praveen > > > > > > Bear in mind that the Garbage Collector doesn't run after a certain amount
of time has passed but when a request for memory for a new object can't be satisfied. But like Mike says you shouldn't really need to worry about what the Garbage Collector is doing unless you are a writing a very time sensitive program. John PS have you considered storing weekReferences to the objects in the HashTable? Show quote "Michael D. Ober" <ober***@.alum.mit.edu.nospam> wrote in message news:etgsG6vXGHA.3972@TK2MSFTNGP04.phx.gbl... > > Don't worry about the Garbage Collector. It will run when it needs to. > If > you are really trying to reduce your application memory footprint, you > need > to call the working set size APIs directly. > > Mike Ober. > > "Praveen" <praveen@newsgroup.nospam> wrote in message > news:%23wsWVtuXGHA.196@TK2MSFTNGP04.phx.gbl... >> >> Hello all, >> >> I am writing a class to cache xml and dataset objects that would be > required >> frequently by my application. I also have a time to check the last access > of >> the obect... If the object is not used for some time I would like to > remove >> it from the cashe to free memmory. I am using hastable to store these >> objects. >> >> What I observe is that even if I remove the object from the hastable the >> memmory is not freed even if I wait a long time (more than 10 mins) to >> for >> the Garbage collection cycle to happen. >> >> To make sure there was an issue with the garbage collection I wrote a >> test >> application. >> >> I declared a class variable for Hashtable >> in one function I am filling the hastable like below >> >> for(int i = 0 ; i < 10000; i++) >> { >> HTT.Add(Guid.NewGuid().ToString(),new string('d',40000)); >> } >> >> In another function I am calling HTT.Clear() to delete the items >> >> during this time I am observing the memmory useage in the taskmanager. >> The >> memmory useage rises as expected in the first function call but does not >> come down after the second function is called. >> >> I waited enough for the GC cycle more thant 10 mins... after the >> HTT.Clear >> function call if I call CG.Colloect(); then memmory was coming down. I >> did >> not want to do that in my app. >> >> please suggest. >> >> Thanks in advance, >> Praveen >> >> >> >> >> >> > > > >Bear in mind that the Garbage Collector doesn't run after a certain amount Yes it does, you don't have to run out of memory for GC to kick in. >of time has passed but when a request for memory for a new object can't be >satisfied. Mattias -- Mattias Sjögren [C# MVP] mattias @ mvps.org http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com Please reply only to the newsgroup. Hi Mattias
It is my understanding that when you allocate a new object it is allocated on the managed heap for the necessary size, and the NextPtr is moved along to the end of the memory just allocated. Then that this continues until watermark levels are reached. If one of these levels is reached then the GC looks to reclaim the memory from Generation 0, if it can't find any here it looks in Generation 1 and if it still can't find it in Generation 2. So with my current understanding it takes an allocation of a new object for this to kick in. Please let me know at which point I have misunderstood. Cheers John Show quote "Mattias Sjögren" <mattias.dont.want.spam@mvps.org> wrote in message news:eW%23qiJyXGHA.4920@TK2MSFTNGP02.phx.gbl... > >Bear in mind that the Garbage Collector doesn't run after a certain > >amount >>of time has passed but when a request for memory for a new object can't be >>satisfied. > > Yes it does, you don't have to run out of memory for GC to kick in. > > > Mattias > > -- > Mattias Sjögren [C# MVP] mattias @ mvps.org > http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com > Please reply only to the newsgroup. John,
The GC will also kick in when the application goes idle and there has been any memory allocations or finalize requests since the last GC cycle. Mike Ober. Show quote "John Davis" <johndavi***@hotmail.com> wrote in message news:efpuLbyXGHA.3660@TK2MSFTNGP04.phx.gbl... > > Hi Mattias > > > > It is my understanding that when you allocate a new object it is allocated > on the managed heap for the necessary size, and the NextPtr is moved along > to the end of the memory just allocated. Then that this continues until > watermark levels are reached. If one of these levels is reached then the GC > looks to reclaim the memory from Generation 0, if it can't find any here it > looks in Generation 1 and if it still can't find it in Generation 2. So > with my current understanding it takes an allocation of a new object for > this to kick in. Please let me know at which point I have misunderstood. > > > > Cheers > > > > John > > > > "Mattias Sjögren" <mattias.dont.want.spam@mvps.org> wrote in message > news:eW%23qiJyXGHA.4920@TK2MSFTNGP02.phx.gbl... > > >Bear in mind that the Garbage Collector doesn't run after a certain > > >amount > >>of time has passed but when a request for memory for a new object can't be > >>satisfied. > > > > Yes it does, you don't have to run out of memory for GC to kick in. > > > > > > Mattias > > > > -- > > Mattias Sjögren [C# MVP] mattias @ mvps.org > > http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com > > Please reply only to the newsgroup. > > >  |
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