GC "Heisenberg" problem in latest CVS bootstrap?

[Brian Rice]

Right. :) Anyway, there's a new alpha set up with some changes by Lee 
in this direction. Feedback and comparisons would be appreciated.

On Dec 9, 2004, at 3:59 PM, Michael Walter wrote:

> "Heisenbug" = what you mean, Heisenberg = guy, where it comes from ;-)
>
> Cheers,
> Michael
>
>
> On Wed, 8 Dec 2004 18:17:10 -0800, Brian Rice <water at tunes.org> wrote:
>> Uh, the consensus is that this is a good idea. I'll accept any
>> reasonable patch in this direction.
>>
>>
>>
>> On Dec 5, 2004, at 1:06 PM, Brian Rice wrote:
>>
>>> Thanks for the analysis. This does seem mostly correct. Lee, any
>>> comments or ideas on design improvements?
>>>
>>> On Dec 4, 2004, at 6:37 PM, Tim Olson wrote:
>>>> On Dec 4, 2004, at 12:46 PM, Brian Rice wrote:
>>>>> It could if there excessive slot additions and removals at some
>>>>> point. I haven't profiled anything to look for this, but
>>>>> numeric.slate's source itself has no abnormal number of such slot
>>>>> manipulations (26). I don't think the lexer, parser, or compiler do
>>>>> this kind of thing dynamically, either.
>>>>
>>>> I don't think there is anything special about "numeric.slate", other
>>>> than it is large (so it shows up dramatically when it takes a long
>>>> time to process), and during my build that's where the free space
>>>> drops to a very small size.   During processing it spent > 90% of 
>>>> its
>>>> time in garbage collection, but GC always found enough free that it
>>>> didn't trigger a heap growth.
>>>>
>>>> To test the idea that it is simply the free space (or more 
>>>> precisely,
>>>> the lack thereof) that is causing this, I performed a large dummy
>>>> allocation just before the bootstrap build:
>>>>
>>>>      Array newSize: 5000000.
>>>>
>>>> The build went much faster; in particular, processing of
>>>> "numeric.slate" was easily 10x faster.
>>>>
>>>> After a number of builds I've not seen a segmentation violation like
>>>> I saw a couple of times during the "slow" build, so I've not been
>>>> able to track down the root cause of that, but I suspect that it was
>>>> caused by some strange condition during the excessive GC.
>>>>
>>>> I think Attila Lendvai's suggestion of triggering early heap growth
>>>> when the free space reclaimed drops below a particular level is a
>>>> good one.
>>>
>>> --
>>> Brian T. Rice
>>> LOGOS Research and Development
>>> http://tunes.org/~water/
>>>
>>>
>> --
>> Brian T. Rice
>> LOGOS Research and Development
>> http://tunes.org/~water/
>>
>>
>
>
--
Brian T. Rice
LOGOS Research and Development
http://tunes.org/~water/