Re: Garbage Collection Issues in long-standing services

Did you ever checked the GC performance counters (using perfmon) to check
whether this is true? The GC is more aggressive than you imagine.
Just check the Gen0 1 and 2 performance counters and you will see that the
collector runs, your problem is that you are holding references to objects
(probably large objects) which you never release, so there is little or
nothing to collect.
By starting another process that allocates memory, your service working set
gets trimmed by the OS, that all that happens.

Willy.

"Larry Herbinaux" <LarryHerbinaux@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
message news:72FFED84-F740-456E-A986-0BB25C18ED39@xxxxxxxxxxxxxxxx
> I'm having issues with garbage collection with my long-standing service
> process. If you could review and point me in the right direction it would
> be
> of great help. If there are any helpful documents that you could point me
> to
> help me control the GC, then that would be great also.
>
> The .Net GC does not cleanup memory of our service process unless it is
> forced to by another process that hogs memory.
> · GC Algorithm - This is an issue because if the GC is not forced into
> doing
> this, it does not aggressively cleanup until the amount of physical memory
> available is very small. I understand why it doesnâ??t want to force
> cleanup
> due to processor efficiency, but it forces applications into conditions
> that
> are not acceptable. It would be nice to be able to hint an upper limit
> for
> an application that helps the GC be more aggressive when required.
> · Race Condition â?? The GC Algorithm causes race conditions because the
> GC is
> not coordinated with our application and our application throws
> OutOfMemoryExceptions. We have very good exception handling that guards
> against unhandled exceptions in the main thread and thread pool threads.
> The
> problem is that we use memory to log these issues so the handlers are
> probably throwing another OutOfMemoryException. We can handle this, but
> the
> point is the OutOfMemoryException cause a transaction to fail.
> · Force GC To Collect - I wrote a Memory Hogger application which when
> run
> will reduce the amount of memory used by the service application from
> 800MB
> to 3MB, so this proves that the GC will cleanup the memory when it truly
> needs it. I noticed that Memory Usage displayed in the Task Manager
> Process
> tab did not add up to the total amount of memory in use, so this means
> that
> the inactive applications probably moved their heap to swap. One concern
> here was that when the Memory Hogger application was terminated, our
> service
> application reclaimed half of its memory and we were not processing
> transactions. Maybe GC just moved it to swap.
> · GC.Collect â?? Using this is not recommended within the application.
> Even
> when this is used, it doesnâ??t make the GC any more aggressive, so I
> agree,
> there is no reason to use it. It would be nice to have the ability to
> make
> the GC more aggressive.
> · CLR Profiler - Iâ??ve used the CLR Profiler to determine what memory is
> not
> being collected. Mostly string and byte arrays. Our service handles TCP
> Connections asynchronously and we reuse the same byte array when receiving
> data for the next asynchronous read. We store a reference to the current
> IAsyncResult for both the asynchronous send and receive requests. The
> state
> object holds the byte array which we are currently not setting to null.
> There isnâ??t a way of canceling the async requests, so we might have to
> explicitly set this to null. I will try this to see if makes a
> difference.
> As for the strings, Iâ??m not sure where the problem is here.
>


.

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