node_cache.h

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/***************************************************************************
 * include/stxxl/bits/containers/btree/node_cache.h
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2006 Roman Dementiev <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#ifndef STXXL_CONTAINERS_BTREE_NODE_CACHE_HEADER
#define STXXL_CONTAINERS_BTREE_NODE_CACHE_HEADER

#include <stxxl/bits/config.h>
#include <stxxl/bits/compat/hash_map.h>
#include <stxxl/bits/io/request.h>
#include <stxxl/bits/mng/block_manager.h>
#include <stxxl/bits/mng/typed_block.h>
#include <stxxl/bits/containers/pager.h>
#include <stxxl/bits/common/error_handling.h>


STXXL_BEGIN_NAMESPACE

// TODO: speedup BID2node_ access using search result iterator in the methods

namespace btree {

template <class NodeType, class BTreeType>
class node_cache : private noncopyable
{
public:
 typedef BTreeType btree_type;
 typedef NodeType node_type;
 typedef typename node_type::block_type block_type;
 typedef typename node_type::bid_type bid_type;
 typedef typename btree_type::key_compare key_compare;

 typedef typename btree_type::alloc_strategy_type alloc_strategy_type;
 typedef stxxl::lru_pager<> pager_type;

private:
 btree_type* btree_;
 key_compare comp_;

/*
 struct bid_comp
 {
 bool operator () (const bid_type & a, const bid_type & b) const
 {
 return (a.storage < b.storage) || ( a.storage == b.storage && a.offset < b.offset);
 }
 };
*/

 struct bid_hash
 {
 size_t operator () (const bid_type& bid) const
 {
 size_t result =
 longhash1(bid.offset + uint64(unsigned_type(bid.storage)));
 return result;
 }
#if STXXL_MSVC
 bool operator () (const bid_type& a, const bid_type& b) const
 {
 return (a.storage < b.storage) || (a.storage == b.storage && a.offset < b.offset);
 }
 enum
 { // parameters for hash table
 bucket_size = 4, // 0 < bucket_size
 min_buckets = 8 // min_buckets = 2 ^^ N, 0 < N
 };
#endif
 };

 std::vector<node_type*> nodes_;
 std::vector<request_ptr> reqs_;
 std::vector<bool> fixed_;
 std::vector<bool> dirty_;
 std::vector<int_type> free_nodes_;
 typedef typename compat_hash_map<bid_type, int_type, bid_hash>::result hash_map_type;

 //typedef std::map<bid_type,int_type,bid_comp> BID2node_type;
 typedef hash_map_type BID2node_type;

 BID2node_type BID2node_;
 pager_type pager_;
 block_manager* bm;
 alloc_strategy_type alloc_strategy_;

 int64 n_found;
 int64 n_not_found;
 int64 n_created;
 int64 n_deleted;
 int64 n_read;
 int64 n_written;
 int64 n_clean_forced;

 // changes btree pointer in all contained iterators
 void change_btree_pointers(btree_type* b)
 {
 typename std::vector<node_type*>::const_iterator it = nodes_.begin();
 for ( ; it != nodes_.end(); ++it)
 {
 (*it)->btree_ = b;
 }
 }

public:
 node_cache(unsigned_type cache_size_in_bytes,
 btree_type* btree__,
 key_compare comp__
 ) :
 btree_(btree__),
 comp_(comp__),
 bm(block_manager::get_instance()),
 n_found(0),
 n_not_found(0),
 n_created(0),
 n_deleted(0),
 n_read(0),
 n_written(0),
 n_clean_forced(0)
 {
 const unsigned_type nnodes = cache_size_in_bytes / block_type::raw_size;
 STXXL_VERBOSE1("btree::node_cache constructor nodes=" << nnodes);
 if (nnodes < 3)
 {
 STXXL_THROW2(std::runtime_error, "btree::node_cache::node_cache", "Too few memory for a node cache (<3)");
 }
 nodes_.reserve(nnodes);
 reqs_.resize(nnodes);
 free_nodes_.reserve(nnodes);
 fixed_.resize(nnodes, false);
 dirty_.resize(nnodes, true);
 for (unsigned_type i = 0; i < nnodes; ++i)
 {
 nodes_.push_back(new node_type(btree_, comp_));
 free_nodes_.push_back(i);
 }

 pager_type tmp_pager(nnodes);
 std::swap(pager_, tmp_pager);
 }

 unsigned_type size() const
 {
 return nodes_.size();
 }

 // returns the number of fixed pages
 unsigned_type nfixed() const
 {
 typename BID2node_type::const_iterator i = BID2node_.begin();
 typename BID2node_type::const_iterator end = BID2node_.end();
 unsigned_type cnt = 0;
 for ( ; i != end; ++i)
 {
 if (fixed_[(*i).second])
 ++cnt;
 }
 return cnt;
 }

 ~node_cache()
 {
 STXXL_VERBOSE1("btree::node_cache destructor addr=" << this);
 typename BID2node_type::const_iterator i = BID2node_.begin();
 typename BID2node_type::const_iterator end = BID2node_.end();
 for ( ; i != end; ++i)
 {
 const unsigned_type p = (*i).second;
 if (reqs_[p].valid())
 reqs_[p]->wait();

 if (dirty_[p])
 nodes_[p]->save();
 }
 for (unsigned_type i = 0; i < size(); ++i)
 delete nodes_[i];
 }

 node_type * get_new_node(bid_type& new_bid)
 {
 ++n_created;

 if (free_nodes_.empty())
 {
 // need to kick a node
 int_type node2kick;
 unsigned_type i = 0;
 const unsigned_type max_tries = size() + 1;
 do
 {
 ++i;
 node2kick = pager_.kick();
 if (i == max_tries)
 {
 STXXL_ERRMSG(
 "The node cache is too small, no node can be kicked out (all nodes are fixed) !");
 STXXL_ERRMSG("Returning NULL node.");
 return NULL;
 }
 pager_.hit(node2kick);
 } while (fixed_[node2kick]);


 if (reqs_[node2kick].valid())
 reqs_[node2kick]->wait();


 node_type& Node = *(nodes_[node2kick]);

 if (dirty_[node2kick])
 {
 Node.save();
 ++n_written;
 }
 else
 ++n_clean_forced;


 //reqs_[node2kick] = request_ptr(); // reset request

 assert(BID2node_.find(Node.my_bid()) != BID2node_.end());
 BID2node_.erase(Node.my_bid());
 bm->new_block(alloc_strategy_, new_bid);

 BID2node_[new_bid] = node2kick;

 Node.init(new_bid);

 dirty_[node2kick] = true;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache get_new_node, need to kick node " << node2kick);

 return &Node;
 }


 int_type free_node = free_nodes_.back();
 free_nodes_.pop_back();
 assert(fixed_[free_node] == false);

 bm->new_block(alloc_strategy_, new_bid);
 BID2node_[new_bid] = free_node;
 node_type& Node = *(nodes_[free_node]);
 Node.init(new_bid);

 // assert(!(reqs_[free_node].valid()));

 pager_.hit(free_node);

 dirty_[free_node] = true;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache get_new_node, free node " << free_node << "available");

 return &Node;
 }


 node_type * get_node(const bid_type& bid, bool fix = false)
 {
 typename BID2node_type::const_iterator it = BID2node_.find(bid);
 ++n_read;

 if (it != BID2node_.end())
 {
 // the node is in cache
 const int_type nodeindex = it->second;
 STXXL_VERBOSE1("btree::node_cache get_node, the node " << nodeindex << "is in cache , fix=" << fix);
 fixed_[nodeindex] = fix;
 pager_.hit(nodeindex);
 dirty_[nodeindex] = true;

 if (reqs_[nodeindex].valid() && !reqs_[nodeindex]->poll())
 reqs_[nodeindex]->wait();


 ++n_found;
 return nodes_[nodeindex];
 }

 ++n_not_found;

 // the node is not in cache
 if (free_nodes_.empty())
 {
 // need to kick a node
 int_type node2kick;
 unsigned_type i = 0;
 const unsigned_type max_tries = size() + 1;
 do
 {
 ++i;
 node2kick = pager_.kick();
 if (i == max_tries)
 {
 STXXL_ERRMSG(
 "The node cache is too small, no node can be kicked out (all nodes are fixed) !");
 STXXL_ERRMSG("Returning NULL node.");
 return NULL;
 }
 pager_.hit(node2kick);
 } while (fixed_[node2kick]);

 if (reqs_[node2kick].valid())
 reqs_[node2kick]->wait();


 node_type& Node = *(nodes_[node2kick]);

 if (dirty_[node2kick])
 {
 Node.save();
 ++n_written;
 }
 else
 ++n_clean_forced;


 BID2node_.erase(Node.my_bid());

 reqs_[node2kick] = Node.load(bid);
 BID2node_[bid] = node2kick;

 fixed_[node2kick] = fix;

 dirty_[node2kick] = true;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache get_node, need to kick node" << node2kick << " fix=" << fix);

 return &Node;
 }

 int_type free_node = free_nodes_.back();
 free_nodes_.pop_back();
 assert(fixed_[free_node] == false);

 node_type& Node = *(nodes_[free_node]);
 reqs_[free_node] = Node.load(bid);
 BID2node_[bid] = free_node;

 pager_.hit(free_node);

 fixed_[free_node] = fix;

 dirty_[free_node] = true;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache get_node, free node " << free_node << "available, fix=" << fix);

 return &Node;
 }

 node_type const * get_const_node(const bid_type& bid, bool fix = false)
 {
 typename BID2node_type::const_iterator it = BID2node_.find(bid);
 ++n_read;

 if (it != BID2node_.end())
 {
 // the node is in cache
 const int_type nodeindex = it->second;
 STXXL_VERBOSE1("btree::node_cache get_node, the node " << nodeindex << "is in cache , fix=" << fix);
 fixed_[nodeindex] = fix;
 pager_.hit(nodeindex);

 if (reqs_[nodeindex].valid() && !reqs_[nodeindex]->poll())
 reqs_[nodeindex]->wait();


 ++n_found;
 return nodes_[nodeindex];
 }

 ++n_not_found;

 // the node is not in cache
 if (free_nodes_.empty())
 {
 // need to kick a node
 int_type node2kick;
 unsigned_type i = 0;
 const unsigned_type max_tries = size() + 1;
 do
 {
 ++i;
 node2kick = pager_.kick();
 if (i == max_tries)
 {
 STXXL_ERRMSG(
 "The node cache is too small, no node can be kicked out (all nodes are fixed) !");
 STXXL_ERRMSG("Returning NULL node.");
 return NULL;
 }
 pager_.hit(node2kick);
 } while (fixed_[node2kick]);

 if (reqs_[node2kick].valid())
 reqs_[node2kick]->wait();


 node_type& Node = *(nodes_[node2kick]);
 if (dirty_[node2kick])
 {
 Node.save();
 ++n_written;
 }
 else
 ++n_clean_forced;


 BID2node_.erase(Node.my_bid());

 reqs_[node2kick] = Node.load(bid);
 BID2node_[bid] = node2kick;

 fixed_[node2kick] = fix;

 dirty_[node2kick] = false;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache get_node, need to kick node" << node2kick << " fix=" << fix);

 return &Node;
 }

 int_type free_node = free_nodes_.back();
 free_nodes_.pop_back();
 assert(fixed_[free_node] == false);

 node_type& Node = *(nodes_[free_node]);
 reqs_[free_node] = Node.load(bid);
 BID2node_[bid] = free_node;

 pager_.hit(free_node);

 fixed_[free_node] = fix;

 dirty_[free_node] = false;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache get_node, free node " << free_node << "available, fix=" << fix);

 return &Node;
 }

 void delete_node(const bid_type& bid)
 {
 typename BID2node_type::const_iterator it = BID2node_.find(bid);
 try
 {
 if (it != BID2node_.end())
 {
 // the node is in the cache
 const int_type nodeindex = it->second;
 STXXL_VERBOSE1("btree::node_cache delete_node " << nodeindex << " from cache.");
 if (reqs_[nodeindex].valid())
 reqs_[nodeindex]->wait();

 //reqs_[nodeindex] = request_ptr(); // reset request
 free_nodes_.push_back(nodeindex);
 BID2node_.erase(bid);
 fixed_[nodeindex] = false;
 }
 ++n_deleted;
 } catch (const io_error& ex)
 {
 bm->delete_block(bid);
 throw io_error(ex.what());
 }
 bm->delete_block(bid);
 }


 void prefetch_node(const bid_type& bid)
 {
 if (BID2node_.find(bid) != BID2node_.end())
 return;


 // the node is not in cache
 if (free_nodes_.empty())
 {
 // need to kick a node
 int_type node2kick;
 unsigned_type i = 0;
 const unsigned_type max_tries = size() + 1;
 do
 {
 ++i;
 node2kick = pager_.kick();
 if (i == max_tries)
 {
 STXXL_ERRMSG(
 "The node cache is too small, no node can be kicked out (all nodes are fixed) !");
 STXXL_ERRMSG("Returning NULL node.");
 return;
 }
 pager_.hit(node2kick);
 } while (fixed_[node2kick]);

 if (reqs_[node2kick].valid())
 reqs_[node2kick]->wait();


 node_type& Node = *(nodes_[node2kick]);

 if (dirty_[node2kick])
 {
 Node.save();
 ++n_written;
 }
 else
 ++n_clean_forced;


 BID2node_.erase(Node.my_bid());

 reqs_[node2kick] = Node.prefetch(bid);
 BID2node_[bid] = node2kick;

 fixed_[node2kick] = false;

 dirty_[node2kick] = false;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache prefetch_node, need to kick node" << node2kick << " ");

 return;
 }

 int_type free_node = free_nodes_.back();
 free_nodes_.pop_back();
 assert(fixed_[free_node] == false);

 node_type& Node = *(nodes_[free_node]);
 reqs_[free_node] = Node.prefetch(bid);
 BID2node_[bid] = free_node;

 pager_.hit(free_node);

 fixed_[free_node] = false;

 dirty_[free_node] = false;

 assert(size() == BID2node_.size() + free_nodes_.size());

 STXXL_VERBOSE1("btree::node_cache prefetch_node, free node " << free_node << "available");

 return;
 }

 void unfix_node(const bid_type& bid)
 {
 assert(BID2node_.find(bid) != BID2node_.end());
 fixed_[BID2node_[bid]] = false;
 STXXL_VERBOSE1("btree::node_cache unfix_node, node " << BID2node_[bid]);
 }

 void swap(node_cache& obj)
 {
 std::swap(comp_, obj.comp_);
 std::swap(nodes_, obj.nodes_);
 std::swap(reqs_, obj.reqs_);
 change_btree_pointers(btree_);
 obj.change_btree_pointers(obj.btree_);
 std::swap(fixed_, obj.fixed_);
 std::swap(free_nodes_, obj.free_nodes_);
 std::swap(BID2node_, obj.BID2node_);
 std::swap(pager_, obj.pager_);
 std::swap(alloc_strategy_, obj.alloc_strategy_);
 std::swap(n_found, obj.n_found);
 std::swap(n_not_found, obj.n_found);
 std::swap(n_created, obj.n_created);
 std::swap(n_deleted, obj.n_deleted);
 std::swap(n_read, obj.n_read);
 std::swap(n_written, obj.n_written);
 std::swap(n_clean_forced, obj.n_clean_forced);
 }

 void print_statistics(std::ostream& o) const
 {
 if (n_read)
 o << "Found blocks : " << n_found << " (" <<
 100. * double(n_found) / double(n_read) << "%)" << std::endl;

 else
 o << "Found blocks : " << n_found << " (" <<
 100 << "%)" << std::endl;

 o << "Not found blocks : " << n_not_found << std::endl;
 o << "Created in the cache blocks : " << n_created << std::endl;
 o << "Deleted blocks : " << n_deleted << std::endl;
 o << "Read blocks : " << n_read << std::endl;
 o << "Written blocks : " << n_written << std::endl;
 o << "Clean blocks forced from the cache: " << n_clean_forced << std::endl;
 }
 void reset_statistics()
 {
 n_found = 0;
 n_not_found = 0;
 n_created = 0;
 n_deleted = 0;
 n_read = 0;
 n_written = 0;
 n_clean_forced = 0;
 }
};

} // namespace btree

STXXL_END_NAMESPACE


namespace std {

template <class NodeType, class BTreeType>
void swap(stxxl::btree::node_cache<NodeType, BTreeType>& a,
 stxxl::btree::node_cache<NodeType, BTreeType>& b)
{
 a.swap(b);
}

} // namespace std

#endif // !STXXL_CONTAINERS_BTREE_NODE_CACHE_HEADER