src/share/vm/utilities/workgroup.hpp

@@ -300,61 +300,10 @@
 // call is serialized and additionally the calculation for the
 // "part" (effectively the worker id for executing the task) is
 // serialized to give each worker a unique "part".  Workers that
 // are not needed for this tasks (i.e., "_active_workers" have
 // been started before it, continue to wait for work.
-//
-// Note on use of FlexibleWorkGang's for GC.
-// There are three places where task completion is determined.
-// In
-//    1) ParallelTaskTerminator::offer_termination() where _n_threads
-//    must be set to the correct value so that count of workers that
-//    have offered termination will exactly match the number
-//    working on the task.  Tasks such as those derived from GCTask
-//    use ParallelTaskTerminator's.  Tasks that want load balancing
-//    by work stealing use this method to gauge completion.
-//    2) SubTasksDone has a variable _n_threads that is used in
-//    all_tasks_completed() to determine completion.  all_tasks_complete()
-//    counts the number of tasks that have been done and then reset
-//    the SubTasksDone so that it can be used again.  When the number of
-//    tasks is set to the number of GC workers, then _n_threads must
-//    be set to the number of active GC workers. G1RootProcessor and
-//    GenCollectedHeap have SubTasksDone.
-//    3) SequentialSubTasksDone has an _n_threads that is used in
-//    a way similar to SubTasksDone and has the same dependency on the
-//    number of active GC workers.  CompactibleFreeListSpace and Space
-//    have SequentialSubTasksDone's.
-//
-// Examples of using SubTasksDone and SequentialSubTasksDone:
-//  G1RootProcessor and GenCollectedHeap::process_roots() use
-//  SubTasksDone* _process_strong_tasks to claim tasks for workers
-//
-//  GenCollectedHeap::gen_process_roots() calls
-//      rem_set()->younger_refs_iterate()
-//  to scan the card table and which eventually calls down into
-//  CardTableModRefBS::par_non_clean_card_iterate_work().  This method
-//  uses SequentialSubTasksDone* _pst to claim tasks.
-//  Both SubTasksDone and SequentialSubTasksDone call their method
-//  all_tasks_completed() to count the number of GC workers that have
-//  finished their work.  That logic is "when all the workers are
-//  finished the tasks are finished".
-//
-//  The pattern that appears  in the code is to set _n_threads
-//  to a value > 1 before a task that you would like executed in parallel
-//  and then to set it to 0 after that task has completed.  A value of
-//  0 is a "special" value in set_n_threads() which translates to
-//  setting _n_threads to 1.
-//
-//  Some code uses _n_termination to decide if work should be done in
-//  parallel.  The notorious possibly_parallel_oops_do() in threads.cpp
-//  is an example of such code.  Look for variable "is_par" for other
-//  examples.
-//
-//  The active_workers is not reset to 0 after a parallel phase.  It's
-//  value may be used in later phases and in one instance at least
-//  (the parallel remark) it has to be used (the parallel remark depends
-//  on the partitioning done in the previous parallel scavenge).
 
 class FlexibleWorkGang: public WorkGang {
   // The currently active workers in this gang.
   // This is a number that is dynamically adjusted
   // and checked in the run_task() method at each invocation.