--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/services/lowMemoryDetector.cpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,386 @@
+/*
+ * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "classfile/vmSymbols.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/interfaceSupport.hpp"
+#include "runtime/java.hpp"
+#include "runtime/javaCalls.hpp"
+#include "runtime/mutex.hpp"
+#include "runtime/mutexLocker.hpp"
+#include "services/lowMemoryDetector.hpp"
+#include "services/management.hpp"
+
+volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;
+volatile jint LowMemoryDetector::_disabled_count = 0;
+
+bool LowMemoryDetector::has_pending_requests() {
+ assert(Service_lock->owned_by_self(), "Must own Service_lock");
+ bool has_requests = false;
+ int num_memory_pools = MemoryService::num_memory_pools();
+ for (int i = 0; i < num_memory_pools; i++) {
+ MemoryPool* pool = MemoryService::get_memory_pool(i);
+ SensorInfo* sensor = pool->usage_sensor();
+ if (sensor != NULL) {
+ has_requests = has_requests || sensor->has_pending_requests();
+ }
+
+ SensorInfo* gc_sensor = pool->gc_usage_sensor();
+ if (gc_sensor != NULL) {
+ has_requests = has_requests || gc_sensor->has_pending_requests();
+ }
+ }
+ return has_requests;
+}
+
+void LowMemoryDetector::process_sensor_changes(TRAPS) {
+ ResourceMark rm(THREAD);
+ HandleMark hm(THREAD);
+
+ // No need to hold Service_lock to call out to Java
+ int num_memory_pools = MemoryService::num_memory_pools();
+ for (int i = 0; i < num_memory_pools; i++) {
+ MemoryPool* pool = MemoryService::get_memory_pool(i);
+ SensorInfo* sensor = pool->usage_sensor();
+ SensorInfo* gc_sensor = pool->gc_usage_sensor();
+ if (sensor != NULL && sensor->has_pending_requests()) {
+ sensor->process_pending_requests(CHECK);
+ }
+ if (gc_sensor != NULL && gc_sensor->has_pending_requests()) {
+ gc_sensor->process_pending_requests(CHECK);
+ }
+ }
+}
+
+// This method could be called from any Java threads
+// and also VMThread.
+void LowMemoryDetector::detect_low_memory() {
+ MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
+
+ bool has_pending_requests = false;
+ int num_memory_pools = MemoryService::num_memory_pools();
+ for (int i = 0; i < num_memory_pools; i++) {
+ MemoryPool* pool = MemoryService::get_memory_pool(i);
+ SensorInfo* sensor = pool->usage_sensor();
+ if (sensor != NULL &&
+ pool->usage_threshold()->is_high_threshold_supported() &&
+ pool->usage_threshold()->high_threshold() != 0) {
+ MemoryUsage usage = pool->get_memory_usage();
+ sensor->set_gauge_sensor_level(usage,
+ pool->usage_threshold());
+ has_pending_requests = has_pending_requests || sensor->has_pending_requests();
+ }
+ }
+
+ if (has_pending_requests) {
+ Service_lock->notify_all();
+ }
+}
+
+// This method could be called from any Java threads
+// and also VMThread.
+void LowMemoryDetector::detect_low_memory(MemoryPool* pool) {
+ SensorInfo* sensor = pool->usage_sensor();
+ if (sensor == NULL ||
+ !pool->usage_threshold()->is_high_threshold_supported() ||
+ pool->usage_threshold()->high_threshold() == 0) {
+ return;
+ }
+
+ {
+ MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
+
+ MemoryUsage usage = pool->get_memory_usage();
+ sensor->set_gauge_sensor_level(usage,
+ pool->usage_threshold());
+ if (sensor->has_pending_requests()) {
+ // notify sensor state update
+ Service_lock->notify_all();
+ }
+ }
+}
+
+// Only called by VMThread at GC time
+void LowMemoryDetector::detect_after_gc_memory(MemoryPool* pool) {
+ SensorInfo* sensor = pool->gc_usage_sensor();
+ if (sensor == NULL ||
+ !pool->gc_usage_threshold()->is_high_threshold_supported() ||
+ pool->gc_usage_threshold()->high_threshold() == 0) {
+ return;
+ }
+
+ {
+ MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
+
+ MemoryUsage usage = pool->get_last_collection_usage();
+ sensor->set_counter_sensor_level(usage, pool->gc_usage_threshold());
+
+ if (sensor->has_pending_requests()) {
+ // notify sensor state update
+ Service_lock->notify_all();
+ }
+ }
+}
+
+// recompute enabled flag
+void LowMemoryDetector::recompute_enabled_for_collected_pools() {
+ bool enabled = false;
+ int num_memory_pools = MemoryService::num_memory_pools();
+ for (int i=0; i<num_memory_pools; i++) {
+ MemoryPool* pool = MemoryService::get_memory_pool(i);
+ if (pool->is_collected_pool() && is_enabled(pool)) {
+ enabled = true;
+ break;
+ }
+ }
+ _enabled_for_collected_pools = enabled;
+}
+
+SensorInfo::SensorInfo() {
+ _sensor_obj = NULL;
+ _sensor_on = false;
+ _sensor_count = 0;
+ _pending_trigger_count = 0;
+ _pending_clear_count = 0;
+}
+
+// When this method is used, the memory usage is monitored
+// as a gauge attribute. Sensor notifications (trigger or
+// clear) is only emitted at the first time it crosses
+// a threshold.
+//
+// High and low thresholds are designed to provide a
+// hysteresis mechanism to avoid repeated triggering
+// of notifications when the attribute value makes small oscillations
+// around the high or low threshold value.
+//
+// The sensor will be triggered if:
+// (1) the usage is crossing above the high threshold and
+// the sensor is currently off and no pending
+// trigger requests; or
+// (2) the usage is crossing above the high threshold and
+// the sensor will be off (i.e. sensor is currently on
+// and has pending clear requests).
+//
+// Subsequent crossings of the high threshold value do not cause
+// any triggers unless the usage becomes less than the low threshold.
+//
+// The sensor will be cleared if:
+// (1) the usage is crossing below the low threshold and
+// the sensor is currently on and no pending
+// clear requests; or
+// (2) the usage is crossing below the low threshold and
+// the sensor will be on (i.e. sensor is currently off
+// and has pending trigger requests).
+//
+// Subsequent crossings of the low threshold value do not cause
+// any clears unless the usage becomes greater than or equal
+// to the high threshold.
+//
+// If the current level is between high and low threshold, no change.
+//
+void SensorInfo::set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold) {
+ assert(Service_lock->owned_by_self(), "Must own Service_lock");
+ assert(high_low_threshold->is_high_threshold_supported(), "just checking");
+
+ bool is_over_high = high_low_threshold->is_high_threshold_crossed(usage);
+ bool is_below_low = high_low_threshold->is_low_threshold_crossed(usage);
+
+ assert(!(is_over_high && is_below_low), "Can't be both true");
+
+ if (is_over_high &&
+ ((!_sensor_on && _pending_trigger_count == 0) ||
+ _pending_clear_count > 0)) {
+ // low memory detected and need to increment the trigger pending count
+ // if the sensor is off or will be off due to _pending_clear_ > 0
+ // Request to trigger the sensor
+ _pending_trigger_count++;
+ _usage = usage;
+
+ if (_pending_clear_count > 0) {
+ // non-zero pending clear requests indicates that there are
+ // pending requests to clear this sensor.
+ // This trigger request needs to clear this clear count
+ // since the resulting sensor flag should be on.
+ _pending_clear_count = 0;
+ }
+ } else if (is_below_low &&
+ ((_sensor_on && _pending_clear_count == 0) ||
+ (_pending_trigger_count > 0 && _pending_clear_count == 0))) {
+ // memory usage returns below the threshold
+ // Request to clear the sensor if the sensor is on or will be on due to
+ // _pending_trigger_count > 0 and also no clear request
+ _pending_clear_count++;
+ }
+}
+
+// When this method is used, the memory usage is monitored as a
+// simple counter attribute. The sensor will be triggered
+// whenever the usage is crossing the threshold to keep track
+// of the number of times the VM detects such a condition occurs.
+//
+// High and low thresholds are designed to provide a
+// hysteresis mechanism to avoid repeated triggering
+// of notifications when the attribute value makes small oscillations
+// around the high or low threshold value.
+//
+// The sensor will be triggered if:
+// - the usage is crossing above the high threshold regardless
+// of the current sensor state.
+//
+// The sensor will be cleared if:
+// (1) the usage is crossing below the low threshold and
+// the sensor is currently on; or
+// (2) the usage is crossing below the low threshold and
+// the sensor will be on (i.e. sensor is currently off
+// and has pending trigger requests).
+void SensorInfo::set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold) {
+ assert(Service_lock->owned_by_self(), "Must own Service_lock");
+ assert(counter_threshold->is_high_threshold_supported(), "just checking");
+
+ bool is_over_high = counter_threshold->is_high_threshold_crossed(usage);
+ bool is_below_low = counter_threshold->is_low_threshold_crossed(usage);
+
+ assert(!(is_over_high && is_below_low), "Can't be both true");
+
+ if (is_over_high) {
+ _pending_trigger_count++;
+ _usage = usage;
+ _pending_clear_count = 0;
+ } else if (is_below_low && (_sensor_on || _pending_trigger_count > 0)) {
+ _pending_clear_count++;
+ }
+}
+
+void SensorInfo::oops_do(OopClosure* f) {
+ f->do_oop((oop*) &_sensor_obj);
+}
+
+void SensorInfo::process_pending_requests(TRAPS) {
+ int pending_count = pending_trigger_count();
+ if (pending_clear_count() > 0) {
+ clear(pending_count, CHECK);
+ } else {
+ trigger(pending_count, CHECK);
+ }
+
+}
+
+void SensorInfo::trigger(int count, TRAPS) {
+ assert(count <= _pending_trigger_count, "just checking");
+ if (_sensor_obj != NULL) {
+ InstanceKlass* sensorKlass = Management::sun_management_Sensor_klass(CHECK);
+ Handle sensor_h(THREAD, _sensor_obj);
+
+ Symbol* trigger_method_signature;
+
+ JavaValue result(T_VOID);
+ JavaCallArguments args(sensor_h);
+ args.push_int((int) count);
+
+ Handle usage_h = MemoryService::create_MemoryUsage_obj(_usage, THREAD);
+ // Call Sensor::trigger(int, MemoryUsage) to send notification to listeners.
+ // When OOME occurs and fails to allocate MemoryUsage object, call
+ // Sensor::trigger(int) instead. The pending request will be processed
+ // but no notification will be sent.
+ if (HAS_PENDING_EXCEPTION) {
+ assert((PENDING_EXCEPTION->is_a(SystemDictionary::OutOfMemoryError_klass())), "we expect only an OOME here");
+ CLEAR_PENDING_EXCEPTION;
+ trigger_method_signature = vmSymbols::int_void_signature();
+ } else {
+ trigger_method_signature = vmSymbols::trigger_method_signature();
+ args.push_oop(usage_h);
+ }
+
+ JavaCalls::call_virtual(&result,
+ sensorKlass,
+ vmSymbols::trigger_name(),
+ trigger_method_signature,
+ &args,
+ THREAD);
+
+ if (HAS_PENDING_EXCEPTION) {
+ // We just clear the OOM pending exception that we might have encountered
+ // in Java's tiggerAction(), and continue with updating the counters since
+ // the Java counters have been updated too.
+ assert((PENDING_EXCEPTION->is_a(SystemDictionary::OutOfMemoryError_klass())), "we expect only an OOME here");
+ CLEAR_PENDING_EXCEPTION;
+ }
+ }
+
+ {
+ // Holds Service_lock and update the sensor state
+ MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
+ assert(_pending_trigger_count > 0, "Must have pending trigger");
+ _sensor_on = true;
+ _sensor_count += count;
+ _pending_trigger_count = _pending_trigger_count - count;
+ }
+}
+
+void SensorInfo::clear(int count, TRAPS) {
+ {
+ // Holds Service_lock and update the sensor state
+ MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
+ if (_pending_clear_count == 0) {
+ // Bail out if we lost a race to set_*_sensor_level() which may have
+ // reactivated the sensor in the meantime because it was triggered again.
+ return;
+ }
+ _sensor_on = false;
+ _sensor_count += count;
+ _pending_clear_count = 0;
+ _pending_trigger_count = _pending_trigger_count - count;
+ }
+
+ if (_sensor_obj != NULL) {
+ InstanceKlass* sensorKlass = Management::sun_management_Sensor_klass(CHECK);
+ Handle sensor(THREAD, _sensor_obj);
+
+ JavaValue result(T_VOID);
+ JavaCallArguments args(sensor);
+ args.push_int((int) count);
+ JavaCalls::call_virtual(&result,
+ sensorKlass,
+ vmSymbols::clear_name(),
+ vmSymbols::int_void_signature(),
+ &args,
+ CHECK);
+ }
+}
+
+//--------------------------------------------------------------
+// Non-product code
+
+#ifndef PRODUCT
+void SensorInfo::print() {
+ tty->print_cr("%s count = " SIZE_FORMAT " pending_triggers = %d pending_clears = %d",
+ (_sensor_on ? "on" : "off"),
+ _sensor_count, _pending_trigger_count, _pending_clear_count);
+}
+
+#endif // PRODUCT