Summary: Attempting to initiate a marking cycle when allocating a humongous object can, if a marking cycle is successfully initiated by another thread, result in the allocating thread spinning until the marking cycle is complete. Eliminate a deadlock between the main ConcurrentMarkThread, the SurrogateLocker thread, the VM thread, and a mutator thread waiting on the SecondaryFreeList_lock (while free regions are going to become available) by not manipulating the pending list lock during the prologue and epilogue of the cleanup pause.
Reviewed-by: brutisso, jcoomes, tonyp

Summary: Revamp of the mechanism that chooses old regions for inclusion in the CSet. It simplifies the code and introduces min and max bounds on the number of old regions added to the CSet at each mixed GC to avoid pathological cases. It also ensures that when we do a mixed GC we'll always find old regions to add to the CSet (i.e., it eliminates the case where a mixed GC will collect no old regions which can happen today).
Reviewed-by: johnc, brutisso

Reviewed-by: kvn, jrose, kevinw, brutisso, twisti, jmasa

Summary: Re-enable survivors during the initial-mark pause. Afterwards, the concurrent marking threads have to scan them and mark everything reachable from them. The next GC will have to wait for the survivors to be scanned.
Reviewed-by: brutisso, johnc

Summary: If we try to schedule an initial-mark GC in order to explicit start a conc mark cycle and it gets pre-empted by antoher GC, we should retry the attempt as long as it's appropriate for the GC cause.
Reviewed-by: brutisso, johnc

Summary: Remove the separate counting phase of concurrent marking by tracking the amount of marked bytes and the cards spanned by marked objects in marking task/worker thread local data structures, which are updated as individual objects are marked.
Reviewed-by: brutisso, tonyp

7132311: G1: assert((s == klass->oop_size(this)) || (Universe::heap()->is_gc_active() && ((is_typeArray()...
Summary: Move the check for when to call collect() to before we do a humongous object allocation
Reviewed-by: stefank, tonyp

Summary: Create a handle and fake an object to make sure that we don't loose the memory we just allocated
Reviewed-by: tonyp, stefank

Summary: During an initial mark pause, signal the Concurrent Mark thread after the pause output from PrintGC/PrintGCDetails is complete.
Reviewed-by: tonyp, brutisso

Reviewed-by: tonyp, johnc

Summary: This change simplifies the interaction between GC and concurrent marking. By disabling survivor spaces during the initial-mark pause we don't need to propagate marks of objects we copy during each GC (since we never need to copy an explicitly marked object).
Reviewed-by: johnc, brutisso

Reviewed-by: brutisso, johnc

Summary: Store the "next chunk start index" in the length field of the to-space object, instead of the from-space object, so that we can always reliably read the size of all from-space objects.
Reviewed-by: johnc, ysr, jmasa

Summary: Parallelize the removal of self forwarding pointers etc. by wrapping in a HeapRegion closure, which is then wrapped inside an AbstractGangTask.
Reviewed-by: tonyp, iveresov

Summary: Introduce a flag that is set when a heap expansion attempt during a GC fails so that we do not consantly attempt to expand the heap when it's going to fail anyway. This not only prevents the excessive ergo output (which is generated when a region allocation fails) but also avoids excessive and ultimately unsuccessful expansion attempts.
Reviewed-by: jmasa, johnc

Summary: Running G1 with ParallelGCThreads==0 results in various crashes and asserts. Most of these are caused by unguarded references to the worker threads array or an incorrect number of active workers.
Reviewed-by: jmasa, tonyp

Summary: Renamed partially-young GCs as mixed and fully-young GCs as young. Change all external output that includes those terms (GC log and GC ergo log) as well as any comments, fields, methods, etc. The changeset also includes very minor code tidying up (added some curly brackets).
Reviewed-by: johnc, brutisso

Summary: Cache workers' calculated starting heap region, used for parallel iteration over the collcection set, for subsequent reuse.
Reviewed-by: tonyp, brutisso

Summary: Change variables representing the number of GC workers to uint from int and size_t.  Change the parameter in work(int i) to work(uint worker_id).
Reviewed-by: brutisso, tonyp

Summary: Fixed G1CollectedHeap::is_in, added tests, cleaned up comments and made Space::is_in pure virtual.
Reviewed-by: brutisso, tonyp, jcoomes

Summary: Parallelize the serial code that was used to mark objects reachable from survivor objects in the collection set. Some minor improvments in the timers used to track the freeing of the collection set along with some tweaks to PrintGCDetails.
Reviewed-by: tonyp, brutisso

Reviewed-by: johnc, brutisso, poonam

Summary: Keep track of all the old regions in the heap with a heap region set.
Reviewed-by: brutisso, johnc

7102445: G1: Unnecessary Resource allocations during RSet scanning
Summary: Add a new per-worker thread line in the PrintGCDetails output. GC Worker Other is the difference between the elapsed time for the parallel phase of the evacuation pause and the sum of the times of the sub-phases (external root scanning, mark stack scanning, RSet updating, RSet scanning, object copying, and termination) for that worker. During RSet scanning, stack allocate DirtyCardToOopClosure objects; allocating these in a resource area was causing abnormally high GC Worker Other times while the worker thread freed ResourceArea chunks.
Reviewed-by: tonyp, jwilhelm, brutisso

Summary: Add a new, separate, pointer to the base of the array of discovered reference lists and use this new pointer in places where we iterate over the entire array.
Reviewed-by: ysr, brutisso

Summary: Removed unused fields and methods, removed the G1CollectoryPolicy_BestRegionsFirst class and folded its functionality into the G1CollectorPolicy class.
Reviewed-by: ysr, brutisso, jcoomes

Summary: Declare GrainBytes, GrainWords, and CardsPerRegion as size_t.
Reviewed-by: jcoomes, tonyp, jmasa

7097053: G1: assert(da ? referent->is_oop() : referent->is_oop_or_null()) failed: referenceProcessor.cpp:1054
Summary: During remembered set scanning, the reference processor could discover a reference object whose referent was in the process of being copied and so may not be completely initialized. Do not perform reference discovery during remembered set scanning.
Reviewed-by: tonyp, ysr

7086533: G1: assert(!_g1->is_obj_dead(obj)): We should not be preserving dead objs: g1CollectedHeap.cpp:3835
Summary: Some objects may not be marked in the event of an evacuation failure in a partially young GC, during a marking cycle. Avoid this situation by not allowing partially young GCs during a marking cycle.
Reviewed-by: tonyp, ysr, brutisso

Summary: Fixed a few inconsistencies in the monitoring data, in particular when reported from jstat.
Reviewed-by: jmasa, brutisso, johnc

Summary: G1 now uses two reference processors - one is used by concurrent marking and the other is used by STW GCs (both full and incremental evacuation pauses). In an evacuation pause, the reference processor is embedded into the closures used to scan objects. Doing so causes causes reference objects to be 'discovered' by the reference processor. At the end of the evacuation pause, these discovered reference objects are processed - preserving (and copying) referent objects (and their reachable graphs) as appropriate.
Reviewed-by: ysr, jwilhelm, brutisso, stefank, tonyp

Summary: As a result of the changes for 7080389, an evacuation failure during an initial mark pause may result in some root objects not being marked. Pass whether the caller is a root scanning closure into the evacuation failure handling code so that the thread that successfully forwards an object to itself also marks the object.
Reviewed-by: ysr, brutisso, tonyp

Summary: Make G1 handle young gen size command line flags more consistently
Reviewed-by: tonyp, jwilhelm

Summary: Fixed inconsistencies and mistakes in the young list target length calculations so that a) the calculated target length is optimal (before, it was not), b) other parameters like max survivor size and max gc locker eden expansion are always consistent with the calculated target length (before, they were not always), and c) the resulting target length was always bound by desired min and max values (before, it was not).
Reviewed-by: brutisso, johnc

Summary: It introduces ergonomic decision logging in G1 for the following heuristics: heap sizing, collection set construction, concurrent cycle initiation, and partially-young GC start/end. The code has a bit of refactoring in a few places to make the decision logging possible. It also replaces alternative ad-hoc logging that we have under different parameters and switches (G1_DEBUG, G1PolicyVerbose).
Reviewed-by: johnc, ysr

Summary: Remove the sentinelRef and let the last Reference in a discovered chain point back to itself.
Reviewed-by: ysr, jmasa

Summary: Refactor code marking code in the evacuation pause copy closures so that an evacuated object is only marked by the thread that successfully copies it.
Reviewed-by: stefank, brutisso, tonyp

Summary: Call {pre,post}_full_gc_dump() before and after a STW full gc of G1CollectedHeap. Also adjusted the prefix message, including the addition of missing whitespace.
Reviewed-by: brutisso, tonyp

Summary: Removed the possibility to turn off generational mode for G1.
Reviewed-by: johnc, ysr, tonyp

Summary: Refactor the allocation code during GC to use the G1AllocRegion abstraction. Use separate subclasses of G1AllocRegion for survivor and old regions. Avoid BOT updates and dirty survivor cards incrementally for the former.
Reviewed-by: brutisso, johnc, ysr