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diff --git a/src/common/PriorityCache.h b/src/common/PriorityCache.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2018 Red Hat
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#ifndef CEPH_PRIORITY_CACHE_H
+#define CEPH_PRIORITY_CACHE_H
+
+#include <stdint.h>
+#include <string>
+#include <vector>
+#include <memory>
+#include <unordered_map>
+#include "common/perf_counters.h"
+#include "include/ceph_assert.h"
+
+namespace PriorityCache {
+  // Reserve 16384 slots for PriorityCache perf counters
+  const int PERF_COUNTER_LOWER_BOUND = 1073741824;
+  const int PERF_COUNTER_MAX_BOUND = 1073758208;
+
+  enum MallocStats {
+    M_FIRST = PERF_COUNTER_LOWER_BOUND,
+    M_TARGET_BYTES,
+    M_MAPPED_BYTES,
+    M_UNMAPPED_BYTES,
+    M_HEAP_BYTES,
+    M_CACHE_BYTES,
+    M_LAST,
+  };
+
+  enum Priority {
+    PRI0,
+    PRI1,
+    PRI2,
+    PRI3,
+    PRI4,
+    PRI5,
+    PRI6,
+    PRI7,
+    PRI8,
+    PRI9,
+    PRI10,
+    PRI11,
+    LAST = PRI11,
+  };
+
+  enum Extra {
+    E_RESERVED = Priority::LAST+1,
+    E_COMMITTED,
+    E_LAST = E_COMMITTED,
+  };
+
+  int64_t get_chunk(uint64_t usage, uint64_t total_bytes);
+
+  struct PriCache {
+    virtual ~PriCache();
+
+    /* Ask the cache to request memory for the given priority. Note that the
+     * cache may ultimately be allocated less memory than it requests here.
+     */
+    virtual int64_t request_cache_bytes(PriorityCache::Priority pri, uint64_t total_cache) const = 0;
+
+    // Get the number of bytes currently allocated to the given priority.
+    virtual int64_t get_cache_bytes(PriorityCache::Priority pri) const = 0;
+
+    // Get the number of bytes currently allocated to all priorities.
+    virtual int64_t get_cache_bytes() const = 0;
+
+    // Allocate bytes for a given priority.
+    virtual void set_cache_bytes(PriorityCache::Priority pri, int64_t bytes) = 0;
+
+    // Allocate additional bytes for a given priority.
+    virtual void add_cache_bytes(PriorityCache::Priority pri, int64_t bytes) = 0;
+
+    /* Commit the current number of bytes allocated to the cache.  Space is
+     * allocated in chunks based on the allocation size and current total size
+     * of memory available for caches. */
+    virtual int64_t commit_cache_size(uint64_t total_cache) = 0;
+
+    /* Get the current number of bytes allocated to the cache. this may be
+     * larger than the value returned by get_cache_bytes as it includes extra
+     * space for future growth. */
+    virtual int64_t get_committed_size() const = 0;
+
+    // Get the ratio of available memory this cache should target.
+    virtual double get_cache_ratio() const = 0;
+
+    // Set the ratio of available memory this cache should target.
+    virtual void set_cache_ratio(double ratio) = 0;
+
+    // Get the name of this cache.
+    virtual std::string get_cache_name() const = 0;
+  };
+
+  class Manager {
+    CephContext* cct = nullptr;
+    PerfCounters* logger;
+    std::unordered_map<std::string, PerfCounters*> loggers;
+    std::unordered_map<std::string, std::vector<int>> indexes;
+    std::unordered_map<std::string, std::shared_ptr<PriCache>> caches;
+
+    // Start perf counter slots after the malloc stats.
+    int cur_index = MallocStats::M_LAST;
+
+    uint64_t min_mem = 0;
+    uint64_t max_mem = 0;
+    uint64_t target_mem = 0;
+    uint64_t tuned_mem = 0;
+    bool reserve_extra;
+
+  public:
+    Manager(CephContext *c, uint64_t min, uint64_t max, uint64_t target,
+            bool reserve_extra);
+    ~Manager();
+    void set_min_memory(uint64_t min) {
+      min_mem = min;
+    }
+    void set_max_memory(uint64_t max) {
+      max_mem = max;
+    }
+    void set_target_memory(uint64_t target) {
+      target_mem = target;
+    }
+    uint64_t get_tuned_mem() const {
+      return tuned_mem;
+    }
+    void insert(const std::string& name, const std::shared_ptr<PriCache> c,
+                bool enable_perf_counters);
+    void erase(const std::string& name);
+    void clear();
+    void tune_memory();
+    void balance();
+
+  private:
+    void balance_priority(int64_t *mem_avail, Priority pri);
+  };
+}
+
+#endif