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6631166: CMS: better heuristics when combatting fragmentation

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Autonomic per-worker free block cache sizing, tunable coalition policies, fixes to per-size block statistics, retuned gain and bandwidth of some feedback loop filters to allow quicker reactivity to abrupt changes in ambient demand, and other heuristics to reduce fragmentation of the CMS old gen. Also tightened some assertions, including those related to locking.

Reviewed-by: jmasa
This commit is contained in:
Y. Srinivas Ramakrishna 2009-12-23 09:23:54 -08:00
parent 1383dc414b
commit 272a6d47bb
26 changed files with 1099 additions and 345 deletions
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39
hotspot/src/share/vm/gc_implementation/shared/allocationStats.hpp
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@ -31,7 +31,7 @@ class AllocationStats VALUE_OBJ_CLASS_SPEC {
// beginning of this sweep:
// Count(end_last_sweep) - Count(start_this_sweep)
// + splitBirths(between) - splitDeaths(between)
// The above number divided by the time since the start [END???] of the
// The above number divided by the time since the end of the
// previous sweep gives us a time rate of demand for blocks
// of this size. We compute a padded average of this rate as
// our current estimate for the time rate of demand for blocks
@ -41,7 +41,7 @@ class AllocationStats VALUE_OBJ_CLASS_SPEC {
// estimates.
AdaptivePaddedAverage _demand_rate_estimate;
ssize_t _desired; // Estimate computed as described above
ssize_t _desired; // Demand stimate computed as described above
ssize_t _coalDesired; // desired +/- small-percent for tuning coalescing
ssize_t _surplus; // count - (desired +/- small-percent),
@ -53,9 +53,9 @@ class AllocationStats VALUE_OBJ_CLASS_SPEC {
ssize_t _coalDeaths; // loss from coalescing
ssize_t _splitBirths; // additional chunks from splitting
ssize_t _splitDeaths; // loss from splitting
size_t _returnedBytes; // number of bytes returned to list.
size_t _returnedBytes; // number of bytes returned to list.
public:
void initialize() {
void initialize(bool split_birth = false) {
AdaptivePaddedAverage* dummy =
new (&_demand_rate_estimate) AdaptivePaddedAverage(CMS_FLSWeight,
CMS_FLSPadding);
@ -67,7 +67,7 @@ class AllocationStats VALUE_OBJ_CLASS_SPEC {
_beforeSweep = 0;
_coalBirths = 0;
_coalDeaths = 0;
_splitBirths = 0;
_splitBirths = split_birth? 1 : 0;
_splitDeaths = 0;
_returnedBytes = 0;
}
@ -75,10 +75,12 @@ class AllocationStats VALUE_OBJ_CLASS_SPEC {
AllocationStats() {
initialize();
}
// The rate estimate is in blocks per second.
void compute_desired(size_t count,
float inter_sweep_current,
float inter_sweep_estimate) {
float inter_sweep_estimate,
float intra_sweep_estimate) {
// If the latest inter-sweep time is below our granularity
// of measurement, we may call in here with
// inter_sweep_current == 0. However, even for suitably small
@ -88,12 +90,31 @@ class AllocationStats VALUE_OBJ_CLASS_SPEC {
// vulnerable to noisy glitches. In such cases, we
// ignore the current sample and use currently available
// historical estimates.
// XXX NEEDS TO BE FIXED
// assert(prevSweep() + splitBirths() >= splitDeaths() + (ssize_t)count, "Conservation Principle");
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// "Total Stock" "Not used at this block size"
if (inter_sweep_current > _threshold) {
ssize_t demand = prevSweep() - count + splitBirths() - splitDeaths();
ssize_t demand = prevSweep() - (ssize_t)count + splitBirths() - splitDeaths();
// XXX NEEDS TO BE FIXED
// assert(demand >= 0, "Demand should be non-negative");
// Defensive: adjust for imprecision in event counting
if (demand < 0) {
demand = 0;
}
float old_rate = _demand_rate_estimate.padded_average();
float rate = ((float)demand)/inter_sweep_current;
_demand_rate_estimate.sample(rate);
_desired = (ssize_t)(_demand_rate_estimate.padded_average()
*inter_sweep_estimate);
float new_rate = _demand_rate_estimate.padded_average();
ssize_t old_desired = _desired;
_desired = (ssize_t)(new_rate * (inter_sweep_estimate
+ CMSExtrapolateSweep
? intra_sweep_estimate
: 0.0));
if (PrintFLSStatistics > 1) {
gclog_or_tty->print_cr("demand: %d, old_rate: %f, current_rate: %f, new_rate: %f, old_desired: %d, new_desired: %d",
demand, old_rate, rate, new_rate, old_desired, _desired);
}
}
}