[space-maps/core] rewrite the core space map to use less memory.

Makefile.in

@@ -87,6 +87,7 @@ SOURCE=\
 	persistent-data/file_utils.cc \
 	persistent-data/hex_dump.cc \
 	persistent-data/space-maps/careful_alloc.cc \
+	persistent-data/space-maps/core.cc \
 	persistent-data/space-maps/disk.cc \
 	persistent-data/space-maps/recursive.cc \
 	persistent-data/space_map.cc \

caching/metadata.cc

@@ -15,7 +15,7 @@ namespace {
 		if (!nr_blocks)
 			throw runtime_error("Metadata is not large enough for superblock.");
 
-		space_map::ptr sm(new core_map(nr_blocks));
+		space_map::ptr sm{create_core_map(nr_blocks)};
 		sm->inc(SUPERBLOCK_LOCATION);
 		transaction_manager::ptr tm(new transaction_manager(bm, sm));
 		return tm;

era/metadata.cc

@@ -13,7 +13,7 @@ namespace {
 		if (!nr_blocks)
 			throw runtime_error("Metadata is not large enough for superblock.");
 
-		space_map::ptr sm(new core_map(nr_blocks));
+		space_map::ptr sm{create_core_map(nr_blocks)};
 		sm->inc(SUPERBLOCK_LOCATION);
 		transaction_manager::ptr tm(new transaction_manager(bm, sm));
 		return tm;

persistent-data/file_utils.cc

@@ -59,7 +59,7 @@ persistent_data::open_tm(block_manager::ptr bm, block_address superblock_locatio
 	if (!nr_blocks)
 		throw runtime_error("Metadata is not large enough for superblock.");
 
-	space_map::ptr sm(new core_map(nr_blocks));
+	space_map::ptr sm{create_core_map(nr_blocks)};
 	sm->inc(superblock_location);
 	transaction_manager::ptr tm(new transaction_manager(bm, sm));
 	return tm;

persistent-data/space-maps/core.cc

@@ -0,0 +1,248 @@
+// Copyright (C) 2020 Red Hat, Inc. All rights reserved.
+//
+// This file is part of the thin-provisioning-tools source.
+//
+// thin-provisioning-tools is free software: you can redistribute it
+// and/or modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation, either version 3 of
+// the License, or (at your option) any later version.
+//
+// thin-provisioning-tools 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 for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with thin-provisioning-tools.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+#include "persistent-data/space-maps/core.h"
+#include "persistent-data/math_utils.h"
+
+#include <stdexcept>
+
+using namespace persistent_data;
+using namespace std;
+
+//----------------------------------------------------------------
+
+namespace {
+	constexpr block_address ENTRIES_PER_WORD = 4 * sizeof(uint64_t);
+
+	class core_map : public checked_space_map {
+	public:
+		typedef std::shared_ptr<core_map> ptr;
+
+		core_map(block_address nr_blocks);
+
+		block_address get_nr_blocks() const override;
+		block_address get_nr_free() const override;
+		ref_t get_count(block_address b) const override;
+		void set_count(block_address b, ref_t c) override;
+		void commit() override;
+		void inc(block_address b, ref_t count) override;
+		void dec(block_address b, ref_t count) override;
+		maybe_block find_free(span_iterator &it) override;
+		bool count_possibly_greater_than_one(block_address b) const override;
+		void extend(block_address extra_blocks) override;
+		void count_metadata(block_counter &bc) const override;
+
+		// FIXME: meaningless, but this class is only used for testing
+		size_t root_size() const override;
+		
+		// FIXME: meaningless, but this class is only used for testing
+		virtual void copy_root(void *dest, size_t len) const override;
+
+		checked_space_map::ptr clone() const override;
+	private:
+		ref_t get_count_(block_address b) const;
+		void set_count_(block_address b, ref_t c);
+		void check_block_(block_address b) const;
+		ref_t lookup_bits_(block_address b) const;
+		void set_bits_(block_address b, ref_t c);
+		ref_t lookup_exception_(block_address b) const;
+
+		block_address nr_blocks_;
+		block_address nr_free_;
+		block_address search_start_;
+
+		std::vector<uint64_t> bits_;
+		std::map<block_address, ref_t> exceptions_;
+
+	};
+
+	core_map::core_map(block_address nr_blocks)
+		: nr_blocks_(nr_blocks),
+		  nr_free_(nr_blocks),
+		  search_start_(0),
+		  bits_(base::div_up(nr_blocks, ENTRIES_PER_WORD)) {
+	}
+
+	block_address
+	core_map::get_nr_blocks() const {
+		return nr_blocks_;
+	}
+
+	block_address
+	core_map::get_nr_free() const {
+		return nr_free_;
+	}
+
+	ref_t
+	core_map::get_count(block_address b) const {
+		check_block_(b);
+		return get_count_(b);
+	}
+
+	void
+	core_map::set_count(block_address b, ref_t c) {
+		check_block_(b);
+		set_count_(b, c);
+	}
+
+	void
+	core_map::commit() {
+	}
+
+	void
+	core_map::inc(block_address b, ref_t count) {
+		check_block_(b);
+		auto old_c = get_count_(b);
+		set_count_(b, old_c + count);
+	}
+
+	void
+	core_map::dec(block_address b, ref_t count) {
+		check_block_(b);
+		auto old_c = get_count_(b);
+		set_count_(b, old_c - count);
+	}
+
+	core_map::maybe_block
+	core_map::find_free(span_iterator &it) {
+		for (maybe_span ms = it.first(); ms; ms = it.next()) {
+			for (block_address b = std::max(search_start_, ms->first); b < ms->second; b++) {
+				check_block_(b);
+				if (!get_count_(b))
+					return maybe_block(b);
+			}
+		}
+
+		return maybe_block();
+	}
+
+	bool
+	core_map::count_possibly_greater_than_one(block_address b) const {
+		return get_count(b) > 1;
+	}
+
+	void
+	core_map::extend(block_address extra_blocks) {
+		throw std::runtime_error("'extend' not implemented");
+	}
+
+	void
+	core_map::count_metadata(block_counter &bc) const {
+	}
+
+	// FIXME: meaningless, but this class is only used for testing
+	size_t
+	core_map::root_size() const {
+		return 0;
+	}
+
+	// FIXME: meaningless, but this class is only used for testing
+	void
+	core_map::copy_root(void *dest, size_t len) const {
+		throw std::runtime_error("'copy root' not implemented");
+	}
+
+	checked_space_map::ptr
+	core_map::clone() const {
+		return ptr(new core_map(*this));
+	}
+
+	void
+	core_map::check_block_(block_address b) const {
+		if (b >= nr_blocks_)
+			throw std::runtime_error("block out of bounds");
+	}
+
+	ref_t
+	core_map::get_count_(block_address b) const {
+		auto c = lookup_bits_(b);
+		if (c == 3)
+			c = lookup_exception_(b);
+
+		return c;
+	}
+
+	void
+	core_map::set_count_(block_address b, ref_t c) {
+		auto old_c = get_count_(b);
+		
+		if (old_c > 2) {
+			if (c > 2)
+				exceptions_[b] = c;
+			else {
+				exceptions_.erase(b);
+				set_bits_(b, c);
+			}
+		} else {
+			if (c > 2) {
+				set_bits_(b, 3);
+				exceptions_.insert(make_pair(b, c));
+			} else
+				set_bits_(b, c);
+		}
+		
+		if (old_c == 0 && c > 0)
+			nr_free_--;
+
+		else if (old_c > 0 && c == 0) {
+			if (b < search_start_)
+				search_start_ = b;
+
+			nr_free_++;
+		}
+	}
+
+	ref_t
+	core_map::lookup_bits_(block_address b) const {
+		block_address word = b / ENTRIES_PER_WORD;
+		block_address shift = (b % ENTRIES_PER_WORD) * 2;
+
+		return (bits_[word] >> shift) & 0b11;
+	}
+
+	void
+	core_map::set_bits_(block_address b, ref_t c) {
+		if (c > 3)
+			throw runtime_error("bad count");
+
+		block_address word = b / ENTRIES_PER_WORD;
+		block_address shift = (b % ENTRIES_PER_WORD) * 2ull;
+
+		auto w = bits_[word] & ~(0b11ull << shift);
+		bits_[word] = w | (((uint64_t) c) << shift);
+	}
+	
+	ref_t
+	core_map::lookup_exception_(block_address b) const {
+		auto it = exceptions_.find(b);
+		if (it == exceptions_.end())
+			throw runtime_error("core space map exception entry missing");
+
+		return it->second;
+	}
+}
+
+//----------------------------------------------------------------
+
+checked_space_map::ptr
+persistent_data::create_core_map(block_address nr_blocks)
+{
+	return checked_space_map::ptr(new core_map(nr_blocks));
+}
+
+//----------------------------------------------------------------

persistent-data/space-maps/core.h

@@ -21,112 +21,12 @@
 
 #include "persistent-data/space_map.h"
 
+#include <map>
+
 //----------------------------------------------------------------
 
 namespace persistent_data {
-	class core_map : public checked_space_map {
-	public:
-		typedef std::shared_ptr<core_map> ptr;
-
-		core_map(block_address nr_blocks)
-			: counts_(nr_blocks, 0),
-			  nr_free_(nr_blocks),
-			  search_start_(0ull) {
-		}
-
-		block_address get_nr_blocks() const {
-			return counts_.size();
-		}
-
-		block_address get_nr_free() const {
-			return nr_free_;
-		}
-
-		ref_t get_count(block_address b) const {
-			return counts_[b];
-		}
-
-		void set_count(block_address b, ref_t c) {
-			if (counts_[b] == 0 && c > 0)
-				nr_free_--;
-
-			else if (counts_[b] > 0 && c == 0) {
-				if (b < search_start_)
-					search_start_ = b;
-
-				nr_free_++;
-			}
-
-			counts_[b] = c;
-		}
-
-		void commit() {
-		}
-
-		void inc(block_address b, ref_t count) override {
-			if (counts_[b] == 0)
-				nr_free_--;
-
-			counts_[b] += count;
-		}
-
-		void dec(block_address b, ref_t count) override {
-			counts_[b] -= count;
-
-			if (counts_[b] == 0) {
-				if (b < search_start_)
-					search_start_ = b;
-				nr_free_++;
-			}
-		}
-
-		maybe_block find_free(span_iterator &it) {
-			for (maybe_span ms = it.first(); ms; ms = it.next()) {
-				if (search_start_ >= ms->second)
-					continue;
-
-				for (block_address b = std::max(search_start_, ms->first); b < ms->second; b++) {
-					if (b >= counts_.size())
-						throw std::runtime_error("block out of bounds");
-
-					if (!counts_[b])
-						return maybe_block(b);
-				}
-			}
-
-			return maybe_block();
-		}
-
-		bool count_possibly_greater_than_one(block_address b) const {
-			return counts_[b] > 1;
-		}
-
-		void extend(block_address extra_blocks) {
-			throw std::runtime_error("'extend' not implemented");
-		}
-
-		void count_metadata(block_counter &bc) const {
-		}
-
-		// FIXME: meaningless, but this class is only used for testing
-		size_t root_size() const {
-			return 0;
-		}
-
-		// FIXME: meaningless, but this class is only used for testing
-		virtual void copy_root(void *dest, size_t len) const {
-			throw std::runtime_error("'copy root' not implemented");
-		}
-
-		checked_space_map::ptr clone() const {
-			return ptr(new core_map(*this));
-		}
-
-	private:
-		std::vector<ref_t> counts_;
-		unsigned nr_free_;
-		block_address search_start_;
-	};
+	checked_space_map::ptr create_core_map(block_address nr_blocks);
 }
 
 //----------------------------------------------------------------

unit-tests/array_block_t.cc

@@ -87,7 +87,7 @@ namespace {
 	transaction_manager::ptr
 	create_tm() {
 		block_manager::ptr bm = create_bm(NR_BLOCKS);
-		space_map::ptr sm(new core_map(NR_BLOCKS));
+		space_map::ptr sm{create_core_map(NR_BLOCKS)};
 		transaction_manager::ptr tm(new transaction_manager(bm, sm));
 		return tm;
 	}

unit-tests/array_t.cc

@@ -38,7 +38,7 @@ namespace {
 	public:
 		ArrayTests()
 			: bm_(new block_manager("./test.data", NR_BLOCKS, 4, block_manager::READ_WRITE)),
-			  sm_(new core_map(NR_BLOCKS)),
+			  sm_(create_core_map(NR_BLOCKS)),
 			  tm_(bm_, sm_) {
 		}
 

unit-tests/bitset_t.cc

@@ -56,7 +56,7 @@ namespace {
 	public:
 		BitsetTests()
 			: bm_(new block_manager("./test.data", NR_BLOCKS, 4, block_manager::READ_WRITE)),
-			  sm_(new core_map(NR_BLOCKS)),
+			  sm_(create_core_map(NR_BLOCKS)),
 			  tm_(bm_, sm_) {
 		}
 

unit-tests/btree_counter_t.cc

@@ -45,7 +45,7 @@ namespace {
 
 	private:
 		space_map::ptr setup_core_map() {
-			space_map::ptr sm(new core_map(NR_BLOCKS));
+			space_map::ptr sm(create_core_map(NR_BLOCKS));
 			sm->inc(SUPERBLOCK);
 			return sm;
 		}

unit-tests/btree_damage_visitor_t.cc

@@ -302,7 +302,7 @@ namespace {
 
 	private:
 		space_map::ptr setup_core_map() {
-			space_map::ptr sm(new core_map(NR_BLOCKS));
+			space_map::ptr sm(create_core_map(NR_BLOCKS));
 			sm->inc(SUPERBLOCK);
 			return sm;
 		}

unit-tests/btree_t.cc

@@ -35,7 +35,7 @@ namespace {
 	public:
 		BtreeTests() 
 			: bm_(new block_manager("./test.data", NR_BLOCKS, 4, block_manager::READ_WRITE)),
-			  sm_(new core_map(NR_BLOCKS)),
+			  sm_(create_core_map(NR_BLOCKS)),
 			  tm_(bm_, sm_) {
 		}
 

unit-tests/space_map_t.cc

@@ -37,14 +37,14 @@ namespace {
 	public:
 		SpaceMapTests()
 			: bm_(new block_manager("./test.data", NR_BLOCKS, MAX_LOCKS, block_manager::READ_WRITE)),
-			  sm_(new core_map(NR_BLOCKS)),
+			  sm_(create_core_map(NR_BLOCKS)),
 			  tm_(bm_, sm_) {
 		}
 
 		struct sm_core_creator {
 			static space_map::ptr
 			create(transaction_manager &tm) {
-				return space_map::ptr(new persistent_data::core_map(NR_BLOCKS));
+				return create_core_map(NR_BLOCKS);
 			}
 		};
 
@@ -52,8 +52,7 @@ namespace {
 			static space_map::ptr
 			create(transaction_manager &tm) {
 				return create_careful_alloc_sm(
-					checked_space_map::ptr(
-						new core_map(NR_BLOCKS)));
+					create_core_map(NR_BLOCKS));
 			}
 		};
 
@@ -61,8 +60,7 @@ namespace {
 			static checked_space_map::ptr
 			create(transaction_manager &tm) {
 				return create_recursive_sm(
-					checked_space_map::ptr(
-						new core_map(NR_BLOCKS)));
+					create_core_map(NR_BLOCKS));
 			}
 		};
 
@@ -279,7 +277,7 @@ TEST_F(SpaceMapTests, test_metadata_and_disk)
 {
 	block_manager::ptr bm(
 		new block_manager("./test.data", NR_BLOCKS, MAX_LOCKS, block_manager::READ_WRITE));
-	space_map::ptr core_sm(new core_map(NR_BLOCKS));
+	space_map::ptr core_sm{create_core_map(NR_BLOCKS)};
 	transaction_manager::ptr tm(new transaction_manager(bm, core_sm));
 	persistent_space_map::ptr metadata_sm = persistent_data::create_metadata_sm(*tm, NR_BLOCKS);
 	copy_space_maps(metadata_sm, core_sm);

unit-tests/test_utils.cc

@@ -21,7 +21,7 @@ void test::zero_block(block_manager::ptr bm, block_address b)
 transaction_manager::ptr
 test::open_temporary_tm(block_manager::ptr bm)
 {
-	space_map::ptr sm(new core_map(bm->get_nr_blocks()));
+	space_map::ptr sm{create_core_map(bm->get_nr_blocks())};
 	transaction_manager::ptr tm(new transaction_manager(bm, sm));
 	return tm;
 }

unit-tests/transaction_manager_t.cc

@@ -34,7 +34,7 @@ namespace {
 	create_tm() {
 		block_manager::ptr bm(
 			new block_manager("./test.data", NR_BLOCKS, MAX_HELD_LOCKS, block_manager::READ_WRITE));
-		space_map::ptr sm(new core_map(NR_BLOCKS));
+		space_map::ptr sm{create_core_map(NR_BLOCKS)};
 		transaction_manager::ptr tm(new transaction_manager(bm, sm));
 		tm->get_sm()->inc(0);
 		return tm;