[Mono-list] Too many heap sections: IncreaseMAXHINCRorMAX_HEAP_SECTS

[Alan McGovern]

Ok.

So the problem is this (as far as i can make out). You're fragmenting the
heap and running out of "free" memory or the GC is just choking on the
amount of data you're spitting out. This is caused by two things.
1) The memorystream increasing in size
2) A hashtable internal to mono constantly increasing in size while
serialisation is taking place.

If you run your testcase with int num = 9000; instead of int num = 15000; it
works fine. So the best advice i can offer is to serialise your data in
smaller chunks for the moment.

Also, i never managed to get an OOM exception when running on MacOS, but the
program did seem to crash/hang.

Alan.



On 5/10/07, Jonathan Gagnon <jonathan.gagnon at croesus.com> wrote:
>
>  I simplified the test a little bit.  I also tried serializing to a
> FileStream instead of a MemoryStream and I got the same result.
>
> I ran the test on Mono Windows and it runs for a while before exiting with
> an OutOfMemoryException.
>
> Jonathan
>
>  ------------------------------
> *De :* mono-list-bounces at lists.ximian.com [mailto:
> mono-list-bounces at lists.ximian.com] *De la part de* Jonathan Gagnon
> *Envoyé :* Thursday, May 10, 2007 2:53 PM
> *À :* 'Alan McGovern'; Mono-list at lists.ximian.com
> *Objet :* Re: [Mono-list] Too many heap sections:
> IncreaseMAXHINCRorMAX_HEAP_SECTS
>
>  Here is a little test that reproduces the problem.  I thought that
> initializing the memory stream to a size bigger than the entire list would
> fix the problem but it only makes it happen less quickly in some cases.
>
> If you play with the numbers in my little test to reduce the size of
> allocated memory, you will notice that it takes longer to run out of memory
> but it still happens after a while.  The way it behaves, it really looks
> like a leak since I have a loop that does the same thing at every run and I
> would expect the memory allocator to be able to reuse the same memory
> instead of growing the heap.
>
> Note that I compiled the test with VS 2005.  I don't know if I could
> reproduce the bug using the mono compiler.
>
> Jonathan
>
>  ------------------------------
> *De :* mono-list-bounces at lists.ximian.com [mailto:
> mono-list-bounces at lists.ximian.com] *De la part de* Alan McGovern
> *Envoyé :* Thursday, May 10, 2007 11:45 AM
> *À :* Mono-list at lists.ximian.com
> *Objet :* [Mono-list] Too many heap sections: Increase
> MAXHINCRorMAX_HEAP_SECTS
>
>  >Also, as a test, could you initialise the memory stream to roughly the
> > size required to store the entire list<T> and see if it works then.
>
>
> > That works fine if I do it that way.  But my problem is that I can't
> > really know in advance how much memory the serialization will use, so it's
> > not really a viable solution.  I'm thinking of trying to split up my list
> > into smaller chunks to see it this could fix the problem by avoiding the
> > large object heap, if there is such a heap in mono.
> >
>
> Sounds like your problem is due to heap fragmentation. The only solution
> is to use a best-guess for the approximate size of the memory stream and
> initialise the memorystream to that to start off with. For example if the
> average size of your class is 68 bytes, then initialise the memorystream to
> array.Length * 68. Or some such thing.
>
> Still, a testcase may prove useful.
>
> Alan.
>
>
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