Mercurial > hg > truffle
diff src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp @ 1359:23b1b27ac76c
6909756: G1: guarantee(G1CollectedHeap::heap()->mark_in_progress(),"Precondition.")
Summary: Make sure that two marking cycles do not overlap, i.e., a new one can only start after the concurrent marking thread finishes all its work. In the fix I piggy-back a couple of minor extra fixes: some general code reformatting for consistency (only around the code I modified), the removal of a field (G1CollectorPolicy::_should_initiate_conc_mark) which doesn't seem to be used at all (it's only set but never read), as well as moving the "is GC locker active" test earlier into the G1 pause / Full GC and using a more appropriate method for it.
Reviewed-by: johnc, jmasa, jcoomes, ysr
author | tonyp |
---|---|
date | Tue, 06 Apr 2010 10:59:45 -0400 |
parents | 56507bcd639e |
children | 7666957bc44d |
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--- a/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp Mon Apr 05 12:19:22 2010 -0400 +++ b/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp Tue Apr 06 10:59:45 2010 -0400 @@ -178,8 +178,8 @@ // so the hack is to do the cast QQQ FIXME _pauses_btwn_concurrent_mark((size_t)G1PausesBtwnConcMark), _n_marks_since_last_pause(0), - _conc_mark_initiated(false), - _should_initiate_conc_mark(false), + _initiate_conc_mark_if_possible(false), + _during_initial_mark_pause(false), _should_revert_to_full_young_gcs(false), _last_full_young_gc(false), @@ -793,7 +793,7 @@ elapsed_time_ms, calculations, full_young_gcs() ? "full" : "partial", - should_initiate_conc_mark() ? " i-m" : "", + during_initial_mark_pause() ? " i-m" : "", _in_marking_window, _in_marking_window_im); #endif // TRACE_CALC_YOUNG_CONFIG @@ -1040,7 +1040,8 @@ set_full_young_gcs(true); _last_full_young_gc = false; _should_revert_to_full_young_gcs = false; - _should_initiate_conc_mark = false; + clear_initiate_conc_mark_if_possible(); + clear_during_initial_mark_pause(); _known_garbage_bytes = 0; _known_garbage_ratio = 0.0; _in_marking_window = false; @@ -1186,7 +1187,8 @@ void G1CollectorPolicy::record_concurrent_mark_init_end_pre(double mark_init_elapsed_time_ms) { _during_marking = true; - _should_initiate_conc_mark = false; + assert(!initiate_conc_mark_if_possible(), "we should have cleared it by now"); + clear_during_initial_mark_pause(); _cur_mark_stop_world_time_ms = mark_init_elapsed_time_ms; } @@ -1257,7 +1259,6 @@ } _n_pauses_at_mark_end = _n_pauses; _n_marks_since_last_pause++; - _conc_mark_initiated = false; } void @@ -1453,17 +1454,24 @@ #endif // PRODUCT if (in_young_gc_mode()) { - last_pause_included_initial_mark = _should_initiate_conc_mark; + last_pause_included_initial_mark = during_initial_mark_pause(); if (last_pause_included_initial_mark) record_concurrent_mark_init_end_pre(0.0); size_t min_used_targ = (_g1->capacity() / 100) * InitiatingHeapOccupancyPercent; - if (cur_used_bytes > min_used_targ) { - if (cur_used_bytes <= _prev_collection_pause_used_at_end_bytes) { - } else if (!_g1->mark_in_progress() && !_last_full_young_gc) { - _should_initiate_conc_mark = true; + + if (!_g1->mark_in_progress() && !_last_full_young_gc) { + assert(!last_pause_included_initial_mark, "invariant"); + if (cur_used_bytes > min_used_targ && + cur_used_bytes > _prev_collection_pause_used_at_end_bytes) { + assert(!during_initial_mark_pause(), "we should not see this here"); + + // Note: this might have already been set, if during the last + // pause we decided to start a cycle but at the beginning of + // this pause we decided to postpone it. That's OK. + set_initiate_conc_mark_if_possible(); } } @@ -1754,7 +1762,7 @@ bool new_in_marking_window = _in_marking_window; bool new_in_marking_window_im = false; - if (_should_initiate_conc_mark) { + if (during_initial_mark_pause()) { new_in_marking_window = true; new_in_marking_window_im = true; } @@ -2173,7 +2181,13 @@ if (predicted_time_ms > _expensive_region_limit_ms) { if (!in_young_gc_mode()) { set_full_young_gcs(true); - _should_initiate_conc_mark = true; + // We might want to do something different here. However, + // right now we don't support the non-generational G1 mode + // (and in fact we are planning to remove the associated code, + // see CR 6814390). So, let's leave it as is and this will be + // removed some time in the future + ShouldNotReachHere(); + set_during_initial_mark_pause(); } else // no point in doing another partial one _should_revert_to_full_young_gcs = true; @@ -2697,6 +2711,50 @@ #endif void +G1CollectorPolicy::decide_on_conc_mark_initiation() { + // We are about to decide on whether this pause will be an + // initial-mark pause. + + // First, during_initial_mark_pause() should not be already set. We + // will set it here if we have to. However, it should be cleared by + // the end of the pause (it's only set for the duration of an + // initial-mark pause). + assert(!during_initial_mark_pause(), "pre-condition"); + + if (initiate_conc_mark_if_possible()) { + // We had noticed on a previous pause that the heap occupancy has + // gone over the initiating threshold and we should start a + // concurrent marking cycle. So we might initiate one. + + bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle(); + if (!during_cycle) { + // The concurrent marking thread is not "during a cycle", i.e., + // it has completed the last one. So we can go ahead and + // initiate a new cycle. + + set_during_initial_mark_pause(); + + // And we can now clear initiate_conc_mark_if_possible() as + // we've already acted on it. + clear_initiate_conc_mark_if_possible(); + } else { + // The concurrent marking thread is still finishing up the + // previous cycle. If we start one right now the two cycles + // overlap. In particular, the concurrent marking thread might + // be in the process of clearing the next marking bitmap (which + // we will use for the next cycle if we start one). Starting a + // cycle now will be bad given that parts of the marking + // information might get cleared by the marking thread. And we + // cannot wait for the marking thread to finish the cycle as it + // periodically yields while clearing the next marking bitmap + // and, if it's in a yield point, it's waiting for us to + // finish. So, at this point we will not start a cycle and we'll + // let the concurrent marking thread complete the last one. + } + } +} + +void G1CollectorPolicy_BestRegionsFirst:: record_collection_pause_start(double start_time_sec, size_t start_used) { G1CollectorPolicy::record_collection_pause_start(start_time_sec, start_used);