Commits on Mar 28, 2016

1. Reworked concurrent mark thread. …

   The primary reason to use a concurrent marking strategy is to reduce the time
   during which the mutator threads are suspended while marking all reachable
   objects.
   
   However, not running the GC synchronously when a memory threshold is reached
   (eg when the Immix region has exhausted available chunks) means that heap
   growth or spill over to another region (eg the Large Object Space) is
   essential.
   
   The growth is undesirable (because right now there is no compaction and growth
   will continue unbounded) and the spill is especially undesirable because the
   LOS collector is much less efficient than the Immix collector.
   
   Since the marker thread is essentially racing the mutator threads, under high
   allocation rates, the marker would be perpetually behind and a lot of growth
   or spill would occur.
   
   Eventually, we'll implement compaction, which will mitigate heap growth. But
   that doesn't solve all the problems. To address these issues, we adhere to the
   following constraints:
   
   1. We don't defer collection. When the first memory threshold is reached, we
   perform synchronous GC and then create the concurrent marker thread.
   2. We respect memory thresholds. We revert to a synchronous collection cycle
   when the concurrent marker cannot keep up with the mutator. Basically, this
   means finishing the GC cycle whenever the threshold is hit.
   3. The concurrent marker restarts its work immediately after finishing a GC
   cycle instead of waiting for memory thresholds to be breached. The concurrent
   marker thread then sleeps for random intervals waiting for the mutators to
   produce more objects to scan.

   

   brixen committed Mar 28, 2016
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   edd398c View commit details

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2. Added stack protection for loading CompiledCode object.

   

   brixen committed Mar 28, 2016
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   9b49b9b View commit details

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3. Added indicator to -v for concurrent GC enabled.

   

   brixen committed Mar 28, 2016
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   aa83a0c View commit details

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