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8008508: CMS does not correctly reduce heap size after a Full GC

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Reviewed-by: johnc, ysr
This commit is contained in:
Jon Masamitsu 2013-02-11 10:31:56 -08:00
parent 90d010120f
commit fabb8c6e25
7 changed files with 269 additions and 230 deletions
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161
hotspot/src/share/vm/memory/generation.cpp
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@ -382,7 +382,9 @@ void Generation::compact() {
CardGeneration::CardGeneration(ReservedSpace rs, size_t initial_byte_size,
int level,
GenRemSet* remset) :
Generation(rs, initial_byte_size, level), _rs(remset)
Generation(rs, initial_byte_size, level), _rs(remset),
_shrink_factor(0), _min_heap_delta_bytes(), _capacity_at_prologue(),
_used_at_prologue()
{
HeapWord* start = (HeapWord*)rs.base();
size_t reserved_byte_size = rs.size();
@ -406,6 +408,9 @@ CardGeneration::CardGeneration(ReservedSpace rs, size_t initial_byte_size,
// the end if we try.
guarantee(_rs->is_aligned(reserved_mr.end()), "generation must be card aligned");
}
_min_heap_delta_bytes = MinHeapDeltaBytes;
_capacity_at_prologue = initial_byte_size;
_used_at_prologue = 0;
}
bool CardGeneration::expand(size_t bytes, size_t expand_bytes) {
@ -457,6 +462,160 @@ void CardGeneration::invalidate_remembered_set() {
}
void CardGeneration::compute_new_size() {
assert(_shrink_factor <= 100, "invalid shrink factor");
size_t current_shrink_factor = _shrink_factor;
_shrink_factor = 0;
// We don't have floating point command-line arguments
// Note: argument processing ensures that MinHeapFreeRatio < 100.
const double minimum_free_percentage = MinHeapFreeRatio / 100.0;
const double maximum_used_percentage = 1.0 - minimum_free_percentage;
// Compute some numbers about the state of the heap.
const size_t used_after_gc = used();
const size_t capacity_after_gc = capacity();
const double min_tmp = used_after_gc / maximum_used_percentage;
size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));
// Don't shrink less than the initial generation size
minimum_desired_capacity = MAX2(minimum_desired_capacity,
spec()->init_size());
assert(used_after_gc <= minimum_desired_capacity, "sanity check");
if (PrintGC && Verbose) {
const size_t free_after_gc = free();
const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");
gclog_or_tty->print_cr(" "
" minimum_free_percentage: %6.2f"
" maximum_used_percentage: %6.2f",
minimum_free_percentage,
maximum_used_percentage);
gclog_or_tty->print_cr(" "
" free_after_gc : %6.1fK"
" used_after_gc : %6.1fK"
" capacity_after_gc : %6.1fK",
free_after_gc / (double) K,
used_after_gc / (double) K,
capacity_after_gc / (double) K);
gclog_or_tty->print_cr(" "
" free_percentage: %6.2f",
free_percentage);
}
if (capacity_after_gc < minimum_desired_capacity) {
// If we have less free space than we want then expand
size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
// Don't expand unless it's significant
if (expand_bytes >= _min_heap_delta_bytes) {
expand(expand_bytes, 0); // safe if expansion fails
}
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" expanding:"
" minimum_desired_capacity: %6.1fK"
" expand_bytes: %6.1fK"
" _min_heap_delta_bytes: %6.1fK",
minimum_desired_capacity / (double) K,
expand_bytes / (double) K,
_min_heap_delta_bytes / (double) K);
}
return;
}
// No expansion, now see if we want to shrink
size_t shrink_bytes = 0;
// We would never want to shrink more than this
size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;
if (MaxHeapFreeRatio < 100) {
const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
const double minimum_used_percentage = 1.0 - maximum_free_percentage;
const double max_tmp = used_after_gc / minimum_used_percentage;
size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
maximum_desired_capacity = MAX2(maximum_desired_capacity,
spec()->init_size());
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" maximum_free_percentage: %6.2f"
" minimum_used_percentage: %6.2f",
maximum_free_percentage,
minimum_used_percentage);
gclog_or_tty->print_cr(" "
" _capacity_at_prologue: %6.1fK"
" minimum_desired_capacity: %6.1fK"
" maximum_desired_capacity: %6.1fK",
_capacity_at_prologue / (double) K,
minimum_desired_capacity / (double) K,
maximum_desired_capacity / (double) K);
}
assert(minimum_desired_capacity <= maximum_desired_capacity,
"sanity check");
if (capacity_after_gc > maximum_desired_capacity) {
// Capacity too large, compute shrinking size
shrink_bytes = capacity_after_gc - maximum_desired_capacity;
// We don't want shrink all the way back to initSize if people call
// System.gc(), because some programs do that between "phases" and then
// we'd just have to grow the heap up again for the next phase. So we
// damp the shrinking: 0% on the first call, 10% on the second call, 40%
// on the third call, and 100% by the fourth call. But if we recompute
// size without shrinking, it goes back to 0%.
shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
if (current_shrink_factor == 0) {
_shrink_factor = 10;
} else {
_shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
}
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" shrinking:"
" initSize: %.1fK"
" maximum_desired_capacity: %.1fK",
spec()->init_size() / (double) K,
maximum_desired_capacity / (double) K);
gclog_or_tty->print_cr(" "
" shrink_bytes: %.1fK"
" current_shrink_factor: %d"
" new shrink factor: %d"
" _min_heap_delta_bytes: %.1fK",
shrink_bytes / (double) K,
current_shrink_factor,
_shrink_factor,
_min_heap_delta_bytes / (double) K);
}
}
}
if (capacity_after_gc > _capacity_at_prologue) {
// We might have expanded for promotions, in which case we might want to
// take back that expansion if there's room after GC. That keeps us from
// stretching the heap with promotions when there's plenty of room.
size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;
expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);
// We have two shrinking computations, take the largest
shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" aggressive shrinking:"
" _capacity_at_prologue: %.1fK"
" capacity_after_gc: %.1fK"
" expansion_for_promotion: %.1fK"
" shrink_bytes: %.1fK",
capacity_after_gc / (double) K,
_capacity_at_prologue / (double) K,
expansion_for_promotion / (double) K,
shrink_bytes / (double) K);
}
}
// Don't shrink unless it's significant
if (shrink_bytes >= _min_heap_delta_bytes) {
shrink(shrink_bytes);
}
}
// Currently nothing to do.
void CardGeneration::prepare_for_verify() {}