Github user JamesPeach commented on a diff in the pull request:
https://github.com/apache/trafficserver/pull/653#discussion_r68599043
--- Diff: iocore/hostdb/P_RefCountCache.h ---
@@ -0,0 +1,896 @@
+/** @file
+
+ A cache (with map-esque interface) for RefCountObjs
+
+ @section license License
+
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+#ifndef _P_RefCountCache_h_
+#define _P_RefCountCache_h_
+
+#include "I_EventSystem.h"
+#include "P_EventSystem.h" // TODO: less? just need ET_TASK
+
+#include <ts/Map.h>
+#include "ts/PriorityQueue.h"
+
+#include <ts/List.h>
+#include <ts/ink_hrtime.h>
+
+#include "ts/Vec.h"
+#include "ts/I_Version.h"
+#include <unistd.h>
+
+#define REFCOUNT_CACHE_EVENT_SYNC REFCOUNT_CACHE_EVENT_EVENTS_START
+
+#define REFCOUNTCACHE_MAGIC_NUMBER 0x0BAD2D9
+#define REFCOUNTCACHE_MAJOR_VERSION 1
+#define REFCOUNTCACHE_MINOR_VERSION 0
+
+// Stats
+enum RefCountCache_Stats {
+ refcountcache_current_items_stat, // current number of items
+ refcountcache_current_size_stat, // current size of cache
+ refcountcache_total_inserts_stat, // total items inserted
+ refcountcache_total_failed_inserts_stat, // total items unable to insert
+ refcountcache_total_lookups_stat, // total get() calls
+ refcountcache_total_hits_stat, // total hits
+
+ // Persistence metrics
+ refcountcache_last_sync_time, // seconds since epoch of last
successful sync
+ refcountcache_last_total_items, // number of items sync last time
+ refcountcache_last_total_size, // total size at last sync
+
+ RefCountCache_Stat_Count
+};
+
+struct RefCountCacheItemMeta {
+ uint64_t key;
+ unsigned int size;
+ ink_time_t expiry_time; // expire time as seconds since epoch
+ RefCountCacheItemMeta(uint64_t key, unsigned int size, int expire_time =
-1) : key(key), size(size), expiry_time(expire_time) {}
+};
+
+// Layer of indirection for the hashmap-- since it needs lots of things
inside of it
+// We'll also use this as the item header, for persisting objects to disk
+class RefCountCacheHashEntry
+{
+public:
+ Ptr<RefCountObj> item;
+ LINK(RefCountCacheHashEntry, item_link);
+
+ PriorityQueueEntry<RefCountCacheHashEntry *> *expiry_entry;
+
+ RefCountCacheItemMeta meta;
+ void
+ set(RefCountObj *i, uint64_t key, unsigned int size, int expire_time)
+ {
+ this->item = make_ptr(i);
+ this->meta = RefCountCacheItemMeta(key, size, expire_time);
+ };
+ // Need a no-argument constructor to use the classAllocator
+ RefCountCacheHashEntry() : expiry_entry(NULL), meta(0, 0){};
+
+ // make these values comparable -- so we can sort them
+ bool
+ operator<(const RefCountCacheHashEntry &v2) const
+ {
+ return this->meta.expiry_time < v2.meta.expiry_time;
+ };
+};
+// Since the hashing values are all fixed size, we can simply use a
classAllocator to avoid mallocs
+extern ClassAllocator<RefCountCacheHashEntry>
refCountCacheHashingValueAllocator;
+extern ClassAllocator<PriorityQueueEntry<RefCountCacheHashEntry *>>
expiryQueueEntry;
+
+struct RefCountCacheHashing {
+ typedef uint64_t ID;
+ typedef uint64_t const Key;
+ typedef RefCountCacheHashEntry Value;
+ typedef DList(RefCountCacheHashEntry, item_link) ListHead;
+
+ static ID
+ hash(Key key)
+ {
+ return key;
+ }
+ static Key
+ key(Value const *value)
+ {
+ return value->meta.key;
+ }
+ static bool
+ equal(Key lhs, Key rhs)
+ {
+ return lhs == rhs;
+ }
+};
+
+// The RefCountCachePartition is simply a map of key -> Ptr<YourClass>
+// We partition the cache to reduce lock contention
+template <class C> class RefCountCachePartition
+{
+public:
+ RefCountCachePartition(unsigned int part_num, uint64_t max_size,
unsigned int max_items, RecRawStatBlock *rsb = NULL);
+ Ptr<C> get(uint64_t key);
+ void put(uint64_t key, C *item, int size = 0, int expire_time = 0);
+ void erase(uint64_t key, int expiry_time = -1);
+
+ void clear();
+ bool is_full();
+ bool reserve(unsigned int);
+
+ const size_t count();
+ void copy(Vec<RefCountCacheHashEntry *> &items);
+
+ typedef typename TSHashTable<RefCountCacheHashing>::iterator
iterator_type;
+ typedef typename TSHashTable<RefCountCacheHashing>::self hash_type;
+ typedef typename TSHashTable<RefCountCacheHashing>::Location
location_type;
+ TSHashTable<RefCountCacheHashing> *get_map();
+
+ Ptr<ProxyMutex> lock; // Lock
+
+private:
+ void metric_inc(RefCountCache_Stats metric_enum, int64_t data);
+
+ unsigned int part_num;
+
+ uint64_t max_size;
+ unsigned int max_items;
+
+ uint64_t size;
+ unsigned int items;
+
+ hash_type item_map;
+
+ PriorityQueue<RefCountCacheHashEntry *> expiry_queue;
+ RecRawStatBlock *rsb;
+};
+
+template <class C>
+RefCountCachePartition<C>::RefCountCachePartition(unsigned int part_num,
uint64_t max_size, unsigned int max_items,
+ RecRawStatBlock *rsb)
+{
+ this->part_num = part_num;
+ this->max_size = max_size;
+ this->max_items = max_items;
+ this->size = 0;
+ this->items = 0;
+ this->rsb = rsb;
+
+ // Initialize lock
+ this->lock = new_ProxyMutex();
+}
+
+template <class C>
+Ptr<C>
+RefCountCachePartition<C>::get(uint64_t key)
+{
+ this->metric_inc(refcountcache_total_lookups_stat, 1);
+ location_type l = this->item_map.find(key);
+ if (l.isValid()) {
+ // found
+ this->metric_inc(refcountcache_total_hits_stat, 1);
+ return make_ptr((C *)l.m_value->item.get());
--- End diff --
Oh I see, you are converting from ``Ptr<RefCountObj>`` to ``Ptr<C>`` where
``C`` inherits from ``RefCountObj``. I guess that this would have to be a
``dynamic_cast`` then :-/
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