[Mono-dev] relaxing the 4GB heap limit (I think implied by LARGE_CONFIG) & bad out-of-memory behavior

[Rodrigo Kumpera]

This is a limitation present on the Boehm collector. Either custom build it
with a larger limit or switch to sgen.


On Wed, Aug 29, 2012 at 6:05 PM, Jonathan Shore <jonathan.shore at gmail.com>wrote:

>
> I have applications that process through terrabytes of timeseries data.
>  Usually I can limit the amount of memory I use in-process, however, from
> time to time I need to deal with data larger than 4GB in size.   I run mono
> both on OSX and linux.   It seems that the LARGE_CONFIG (which is not even
> the default), maxes out at something close to 4GB of heap.     What would
> it take to relax this so can use more of a 64bit memory space?
>
> In *libgc/include/private/gc_priv.h*, there seems to be a hastable of
> heap pages, indexed by up to 20 bits in the LARGE_CONFIG compilation.  The
> comment indicates that the 2097151 possible entries corresponds to roughly
> 4GB +/- of heap.
>
> Regardless of limitations build into the memory model, the mono runtime
> has the *bad behavior of crashing* when the maximum # of heap pages is
> reached *instead of throwing OutOfMemoryException*.  Particularly for
> production services it would be useful to catch, say, a condition where
> most of the memory is used and throw an exception so that the application
> can exit or clean up gracefully.
>
> Thoughts on this?
>
> Jonathan
>
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