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

[Greg Young]

We have been experiencing crashes as well on large heaps. What can we do to
help with this issue?

On Thursday, August 30, 2012, Jonathan Shore wrote:

> Ok, thanks.  sgen fails for me for non-trivial programs (the VM crashes in
> 2.10.9 and 2.11.3 in different ways on both OSX and Linux).   I'll post a
> bug report to bugzilla in a few.
>
> On Aug 29, 2012, at 5:35 PM, Rodrigo Kumpera wrote:
>
> 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<javascript:_e({}, 'cvml', '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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>>
>
>

-- 
Le doute n'est pas une condition agréable, mais la certitude est absurde.
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