47 // For full GC, generation is always Global.
48 //
49 // Note that the size of the chosen collection set is proportional to the relevant generation's collection set.
50 // Note also that the generation size may change following selection of the collection set, as a side effect
51 // of evacuation. Evacuation may promote objects, causing old to grow and young to shrink. Or this may be a
52 // mixed evacuation. When old regions are evacuated, this typically allows young to expand. In all of these
53 // various scenarios, the purpose of asking is_good_progress() is to determine if there is enough memory available
54 // within young generation to justify making an attempt to perform a concurrent collection. For this reason, we'll
55 // use the current size of the generation (which may not be different than when the collection set was chosen) to
56 // assess how much free memory we require in order to consider the most recent GC to have had good progress.
57
58 bool ShenandoahMetricsSnapshot::is_good_progress(ShenandoahGeneration* generation) {
59 // Under the critical threshold?
60 ShenandoahFreeSet* free_set = _heap->free_set();
61 size_t free_actual = free_set->available();
62 assert(free_actual != ShenandoahFreeSet::FreeSetUnderConstruction, "Avoid this race");
63
64 // ShenandoahCriticalFreeThreshold is expressed as a percentage. We multiple this percentage by 1/100th
65 // of the generation capacity to determine whether the available memory within the generation exceeds the
66 // critical threshold.
67 size_t free_expected = (generation->max_capacity() / 100) * ShenandoahCriticalFreeThreshold;
68
69 bool prog_free = free_actual >= free_expected;
70 log_info(gc, ergo)("%s progress for free space: %zu%s, need %zu%s",
71 prog_free ? "Good" : "Bad",
72 byte_size_in_proper_unit(free_actual), proper_unit_for_byte_size(free_actual),
73 byte_size_in_proper_unit(free_expected), proper_unit_for_byte_size(free_expected));
74 if (!prog_free) {
75 return false;
76 }
77
78 // Freed up enough?
79 size_t progress_actual = (_used_before > _used_after) ? _used_before - _used_after : 0;
80 size_t progress_expected = ShenandoahHeapRegion::region_size_bytes();
81 bool prog_used = progress_actual >= progress_expected;
82 log_info(gc, ergo)("%s progress for used space: %zu%s, need %zu%s",
83 prog_used ? "Good" : "Bad",
84 byte_size_in_proper_unit(progress_actual), proper_unit_for_byte_size(progress_actual),
85 byte_size_in_proper_unit(progress_expected), proper_unit_for_byte_size(progress_expected));
86 if (prog_used) {
87 return true;
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47 // For full GC, generation is always Global.
48 //
49 // Note that the size of the chosen collection set is proportional to the relevant generation's collection set.
50 // Note also that the generation size may change following selection of the collection set, as a side effect
51 // of evacuation. Evacuation may promote objects, causing old to grow and young to shrink. Or this may be a
52 // mixed evacuation. When old regions are evacuated, this typically allows young to expand. In all of these
53 // various scenarios, the purpose of asking is_good_progress() is to determine if there is enough memory available
54 // within young generation to justify making an attempt to perform a concurrent collection. For this reason, we'll
55 // use the current size of the generation (which may not be different than when the collection set was chosen) to
56 // assess how much free memory we require in order to consider the most recent GC to have had good progress.
57
58 bool ShenandoahMetricsSnapshot::is_good_progress(ShenandoahGeneration* generation) {
59 // Under the critical threshold?
60 ShenandoahFreeSet* free_set = _heap->free_set();
61 size_t free_actual = free_set->available();
62 assert(free_actual != ShenandoahFreeSet::FreeSetUnderConstruction, "Avoid this race");
63
64 // ShenandoahCriticalFreeThreshold is expressed as a percentage. We multiple this percentage by 1/100th
65 // of the generation capacity to determine whether the available memory within the generation exceeds the
66 // critical threshold.
67 size_t free_expected = (ShenandoahHeap::heap()->soft_max_capacity() / 100) * ShenandoahCriticalFreeThreshold;
68
69 bool prog_free = free_actual >= free_expected;
70 log_info(gc, ergo)("%s progress for free space: %zu%s, need %zu%s",
71 prog_free ? "Good" : "Bad",
72 byte_size_in_proper_unit(free_actual), proper_unit_for_byte_size(free_actual),
73 byte_size_in_proper_unit(free_expected), proper_unit_for_byte_size(free_expected));
74 if (!prog_free) {
75 return false;
76 }
77
78 // Freed up enough?
79 size_t progress_actual = (_used_before > _used_after) ? _used_before - _used_after : 0;
80 size_t progress_expected = ShenandoahHeapRegion::region_size_bytes();
81 bool prog_used = progress_actual >= progress_expected;
82 log_info(gc, ergo)("%s progress for used space: %zu%s, need %zu%s",
83 prog_used ? "Good" : "Bad",
84 byte_size_in_proper_unit(progress_actual), proper_unit_for_byte_size(progress_actual),
85 byte_size_in_proper_unit(progress_expected), proper_unit_for_byte_size(progress_expected));
86 if (prog_used) {
87 return true;
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