truffle: src/share/vm/runtime/sweeper.cpp comparison

8029091: Bug in calculation of code cache sweeping interval Summary: Use signed data type so that no underflow can happen Reviewed-by: kvn, roland

comparison

equal deleted inserted replaced

-:050a626a8895
+:d49557091d18
 //                                              As a result, we invoke the sweeper after
 //                                              15 invocations of 'mark_active_nmethods.
 // 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;
+const int time_since_last_sweep = _time_counter - _last_sweep;
-double wait_until_next_sweep = (ReservedCodeCacheSize / (16 * M)) - time_since_last_sweep -
+// ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
-CodeCache::reverse_free_ratio();
+// 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;
 }
 }

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