[Haskell-cafe] Aeson memory use

Vanessa McHale vanessa.mchale at iohk.io
Thu Aug 9 14:38:23 UTC 2018

Well, the problem with that is that in a lazy language, the "parsing
stage" may not be as clearly distinguished as you suggest. Simply
forcing the evaluation of all THUNKs is not what happens in the actual

On 08/09/2018 07:57 AM, Lana Black wrote:
> On 08/08/2018 08:24 PM, Vanessa McHale wrote:
>> I'm not 100% sure it's applicable in your case, but perhaps trying
>> threadscope would be a good idea?
>> Based on the heap profile, I'm guessing that most of the allocations are
>> due to slicing ByteStrings up. What happens when you try to read a map
>> of Integers?
> Parsing a 'Map Int Int' gives a similar picture, with slightly lower
> memory use due to the absence of [Text]. However, it is still in the
> hundreds of megabytes for a 10 megabyte file. I also noticed that Map
> itself contributes significantly to the memory footprint.
>> I'd also note that your example uses evaluate and performGC which isn't
>> entirely realistic and thus may not actually correspond to the
>> performance of the application in practice. I gather it *was* a problem
>> in practice but nonetheless it's always good to benchmark the right
>> thing.
> Removing evaluate and force adds THUNKs to the heap profile, which is
> probably the wrong thing to benchmark anyway. What I was trying to
> benchmark was the memory footprint during the parsing stage and after
> it, when only the resulting data should be residing in memory.
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