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8029091: Bug in calculation of code cache sweeping interval

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Use signed data type so that no underflow can happen

Reviewed-by: kvn, roland
This commit is contained in:
Albert Noll 2013-12-17 08:31:06 +01:00
parent 343c8d34a8
commit 2656f6d603
1 changed files with 8 additions and 3 deletions
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11
hotspot/src/share/vm/runtime/sweeper.cpp
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@ -257,9 +257,14 @@ void NMethodSweeper::possibly_sweep() {
// Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula
// computes: (256 / 16) - 10 = 6.
if (!_should_sweep) {
int time_since_last_sweep = _time_counter - _last_sweep;
double wait_until_next_sweep = (ReservedCodeCacheSize / (16 * M)) - time_since_last_sweep -
CodeCache::reverse_free_ratio();
const int time_since_last_sweep = _time_counter - _last_sweep;
// ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
// since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
// an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
// value) that disables the intended periodic sweeps.
const int max_wait_time = ReservedCodeCacheSize / (16 * M);
double wait_until_next_sweep = max_wait_time - time_since_last_sweep - CodeCache::reverse_free_ratio();
assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
_should_sweep = true;