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src/share/vm/jfr/leakprofiler/chains/edgeUtils.cpp
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rev 9055 : 8214542: JFR: Old Object Sample event slow on a deep heap in debug builds
Reviewed-by: egahlin, rwestberg
@@ -1,7 +1,7 @@
/*
- * Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2019, 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.
@@ -36,15 +36,11 @@
bool EdgeUtils::is_leak_edge(const Edge& edge) {
return (const Edge*)edge.pointee()->mark() == &edge;
}
-bool EdgeUtils::is_root(const Edge& edge) {
- return edge.is_root();
-}
-
-static int field_offset(const Edge& edge) {
+static int field_offset(const StoredEdge& edge) {
assert(!edge.is_root(), "invariant");
const oop ref_owner = edge.reference_owner();
assert(ref_owner != NULL, "invariant");
const oop* reference = UnifiedOop::decode(edge.reference());
assert(reference != NULL, "invariant");
@@ -54,11 +50,11 @@
const int offset = (int)pointer_delta(reference, ref_owner, sizeof(char));
assert(offset < (ref_owner->size() * HeapWordSize), "invariant");
return offset;
}
-static const InstanceKlass* field_type(const Edge& edge) {
+static const InstanceKlass* field_type(const StoredEdge& edge) {
assert(!edge.is_root() || !EdgeUtils::is_array_element(edge), "invariant");
return (const InstanceKlass*)edge.reference_owner_klass();
}
const Symbol* EdgeUtils::field_name_symbol(const Edge& edge) {
@@ -136,177 +132,20 @@
const Edge* parent = current->parent();
while (parent != NULL) {
current = parent;
parent = current->parent();
}
+ assert(current != NULL, "invariant");
return current;
}
-// The number of references associated with the leak node;
-// can be viewed as the leak node "context".
-// Used to provide leak context for a "capped/skipped" reference chain.
-static const size_t leak_context = 100;
-
-// The number of references associated with the root node;
-// can be viewed as the root node "context".
-// Used to provide root context for a "capped/skipped" reference chain.
-static const size_t root_context = 100;
-
-// A limit on the reference chain depth to be serialized,
-static const size_t max_ref_chain_depth = leak_context + root_context;
-
-const RoutableEdge* skip_to(const RoutableEdge& edge, size_t skip_length) {
- const RoutableEdge* current = &edge;
- const RoutableEdge* parent = current->physical_parent();
+const Edge* EdgeUtils::ancestor(const Edge& edge, size_t distance) {
+ const Edge* current = &edge;
+ const Edge* parent = current->parent();
size_t seek = 0;
- while (parent != NULL && seek != skip_length) {
+ while (parent != NULL && seek != distance) {
seek++;
current = parent;
- parent = parent->physical_parent();
- }
- return current;
-}
-
-#ifdef ASSERT
-static void validate_skip_target(const RoutableEdge* skip_target) {
- assert(skip_target != NULL, "invariant");
- assert(skip_target->distance_to_root() + 1 == root_context, "invariant");
- assert(skip_target->is_sentinel(), "invariant");
-}
-
-static void validate_new_skip_edge(const RoutableEdge* new_skip_edge, const RoutableEdge* last_skip_edge, size_t adjustment) {
- assert(new_skip_edge != NULL, "invariant");
- assert(new_skip_edge->is_skip_edge(), "invariant");
- if (last_skip_edge != NULL) {
- const RoutableEdge* const target = skip_to(*new_skip_edge->logical_parent(), adjustment);
- validate_skip_target(target->logical_parent());
- return;
+ parent = parent->parent();
}
- assert(last_skip_edge == NULL, "invariant");
- // only one level of logical indirection
- validate_skip_target(new_skip_edge->logical_parent());
-}
-#endif // ASSERT
-
-static void install_logical_route(const RoutableEdge* new_skip_edge, size_t skip_target_distance) {
- assert(new_skip_edge != NULL, "invariant");
- assert(!new_skip_edge->is_skip_edge(), "invariant");
- assert(!new_skip_edge->processed(), "invariant");
- const RoutableEdge* const skip_target = skip_to(*new_skip_edge, skip_target_distance);
- assert(skip_target != NULL, "invariant");
- new_skip_edge->set_skip_edge(skip_target);
- new_skip_edge->set_skip_length(skip_target_distance);
- assert(new_skip_edge->is_skip_edge(), "invariant");
- assert(new_skip_edge->logical_parent() == skip_target, "invariant");
-}
-
-static const RoutableEdge* find_last_skip_edge(const RoutableEdge& edge, size_t& distance) {
- assert(distance == 0, "invariant");
- const RoutableEdge* current = &edge;
- while (current != NULL) {
- if (current->is_skip_edge() && current->skip_edge()->is_sentinel()) {
return current;
- }
- current = current->physical_parent();
- ++distance;
- }
- return current;
-}
-
-static void collapse_overlapping_chain(const RoutableEdge& edge,
- const RoutableEdge* first_processed_edge,
- size_t first_processed_distance) {
- assert(first_processed_edge != NULL, "invariant");
- // first_processed_edge is already processed / written
- assert(first_processed_edge->processed(), "invariant");
- assert(first_processed_distance + 1 <= leak_context, "invariant");
-
- // from this first processed edge, attempt to fetch the last skip edge
- size_t last_skip_edge_distance = 0;
- const RoutableEdge* const last_skip_edge = find_last_skip_edge(*first_processed_edge, last_skip_edge_distance);
- const size_t distance_discovered = first_processed_distance + last_skip_edge_distance + 1;
-
- if (distance_discovered <= leak_context || (last_skip_edge == NULL && distance_discovered <= max_ref_chain_depth)) {
- // complete chain can be accommodated without modification
- return;
- }
-
- // backtrack one edge from existing processed edge
- const RoutableEdge* const new_skip_edge = skip_to(edge, first_processed_distance - 1);
- assert(new_skip_edge != NULL, "invariant");
- assert(!new_skip_edge->processed(), "invariant");
- assert(new_skip_edge->parent() == first_processed_edge, "invariant");
-
- size_t adjustment = 0;
- if (last_skip_edge != NULL) {
- assert(leak_context - 1 > first_processed_distance - 1, "invariant");
- adjustment = leak_context - first_processed_distance - 1;
- assert(last_skip_edge_distance + 1 > adjustment, "invariant");
- install_logical_route(new_skip_edge, last_skip_edge_distance + 1 - adjustment);
- } else {
- install_logical_route(new_skip_edge, last_skip_edge_distance + 1 - root_context);
- new_skip_edge->logical_parent()->set_skip_length(1); // sentinel
- }
-
- DEBUG_ONLY(validate_new_skip_edge(new_skip_edge, last_skip_edge, adjustment);)
-}
-
-static void collapse_non_overlapping_chain(const RoutableEdge& edge,
- const RoutableEdge* first_processed_edge,
- size_t first_processed_distance) {
- assert(first_processed_edge != NULL, "invariant");
- assert(!first_processed_edge->processed(), "invariant");
- // this implies that the first "processed" edge is the leak context relative "leaf"
- assert(first_processed_distance + 1 == leak_context, "invariant");
-
- const size_t distance_to_root = edge.distance_to_root();
- if (distance_to_root + 1 <= max_ref_chain_depth) {
- // complete chain can be accommodated without constructing a skip edge
- return;
- }
-
- install_logical_route(first_processed_edge, distance_to_root + 1 - first_processed_distance - root_context);
- first_processed_edge->logical_parent()->set_skip_length(1); // sentinel
-
- DEBUG_ONLY(validate_new_skip_edge(first_processed_edge, NULL, 0);)
-}
-
-static const RoutableEdge* processed_edge(const RoutableEdge& edge, size_t& distance) {
- assert(distance == 0, "invariant");
- const RoutableEdge* current = &edge;
- while (current != NULL && distance < leak_context - 1) {
- if (current->processed()) {
- return current;
- }
- current = current->physical_parent();
- ++distance;
- }
- assert(distance <= leak_context - 1, "invariant");
- return current;
-}
-
-/*
- * Some vocabulary:
- * -----------
- * "Context" is an interval in the chain, it is associcated with an edge and it signifies a number of connected edges.
- * "Processed / written" means an edge that has already been serialized.
- * "Skip edge" is an edge that contains additional information for logical routing purposes.
- * "Skip target" is an edge used as a destination for a skip edge
- */
-void EdgeUtils::collapse_chain(const RoutableEdge& edge) {
- assert(is_leak_edge(edge), "invariant");
-
- // attempt to locate an already processed edge inside current leak context (if any)
- size_t first_processed_distance = 0;
- const RoutableEdge* const first_processed_edge = processed_edge(edge, first_processed_distance);
- if (first_processed_edge == NULL) {
- return;
- }
-
- if (first_processed_edge->processed()) {
- collapse_overlapping_chain(edge, first_processed_edge, first_processed_distance);
- } else {
- collapse_non_overlapping_chain(edge, first_processed_edge, first_processed_distance);
- }
-
- assert(edge.logical_distance_to_root() + 1 <= max_ref_chain_depth, "invariant");
}
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