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Re: [RFA] update ggc_min_heapsize_heuristic()


On 10/04/17 12:06, Segher Boessenkool wrote:
> On Mon, Apr 10, 2017 at 12:52:15PM +0200, Markus Trippelsdorf wrote:
>>>  --param ggc-min-heapsize=131072
>>> 11264.89user 311.88system 24:18.69elapsed 793%CPU (0avgtext+0avgdata 1265352maxresident)k
>>
>>  --param ggc-min-heapsize=262144
>> 10778.52user 336.34system 23:15.71elapsed 796%CPU (0avgtext+0avgdata 1277468maxresident)k 
>>
>>>  --param ggc-min-heapsize=393216
>>> 10655.42user 347.92system 23:01.17elapsed 796%CPU (0avgtext+0avgdata 1280476maxresident)k
>>>
>>>  --param ggc-min-heapsize=524288
>>> 10565.33user 352.90system 22:51.33elapsed 796%CPU (0avgtext+0avgdata 1506348maxresident)k
> 
> So 256MB gets 70% of the speed gain of 512MB, but for only 5% of the cost
> in RSS.  384MB is an even better tradeoff for this testcase (but smaller
> is safer).
> 
> Can the GC not tune itself better?  Or, not cost so much in the first
> place ;-)
> 
> 
> Segher
> 

I think the idea of a fixed number is that it avoids the problem of bug
reproducibility in the case of memory corruption.

R.


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