Move CompactionStrategy from searchcommon to vespalib.

3 files changed, 70 insertions, 0 deletions

diff --git a/vespalib/src/vespa/vespalib/datastore/CMakeLists.txt b/vespalib/src/vespa/vespalib/datastore/CMakeLists.txt
index 9b796c62232..c36077e4dd0 100644
--- a/vespalib/src/vespa/vespalib/datastore/CMakeLists.txt
+++ b/vespalib/src/vespa/vespalib/datastore/CMakeLists.txt
@@ -5,6 +5,7 @@ vespa_add_library(vespalib_vespalib_datastore OBJECT
     array_store_config.cpp
     buffer_type.cpp
     bufferstate.cpp
+    compaction_strategy.cpp
     datastore.cpp
     datastorebase.cpp
     entryref.cpp
diff --git a/vespalib/src/vespa/vespalib/datastore/compaction_strategy.cpp b/vespalib/src/vespa/vespalib/datastore/compaction_strategy.cpp
new file mode 100644
index 00000000000..43da1837427
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/datastore/compaction_strategy.cpp
@@ -0,0 +1,16 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "compaction_strategy.h"
+#include <iostream>
+
+namespace vespalib::datastore {
+
+std::ostream& operator<<(std::ostream& os, const CompactionStrategy& compaction_strategy)
+{
+    os << "{maxDeadBytesRatio=" << compaction_strategy.getMaxDeadBytesRatio() <<
+        ", maxDeadAddressSpaceRatio=" << compaction_strategy.getMaxDeadAddressSpaceRatio() <<
+        "}";
+    return os;
+}
+
+}
diff --git a/vespalib/src/vespa/vespalib/datastore/compaction_strategy.h b/vespalib/src/vespa/vespalib/datastore/compaction_strategy.h
new file mode 100644
index 00000000000..06d54786122
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/datastore/compaction_strategy.h
@@ -0,0 +1,53 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <iosfwd>
+
+namespace vespalib::datastore {
+
+/*
+ * Class describing compaction strategy for a compactable data structure.
+ */
+class CompactionStrategy
+{
+private:
+    double _maxDeadBytesRatio; // Max ratio of dead bytes before compaction
+    double _maxDeadAddressSpaceRatio; // Max ratio of dead address space before compaction
+public:
+    CompactionStrategy() noexcept
+        : _maxDeadBytesRatio(0.05),
+          _maxDeadAddressSpaceRatio(0.2)
+    {
+    }
+    CompactionStrategy(double maxDeadBytesRatio, double maxDeadAddressSpaceRatio) noexcept
+        : _maxDeadBytesRatio(maxDeadBytesRatio),
+          _maxDeadAddressSpaceRatio(maxDeadAddressSpaceRatio)
+    {
+    }
+    double getMaxDeadBytesRatio() const { return _maxDeadBytesRatio; }
+    double getMaxDeadAddressSpaceRatio() const { return _maxDeadAddressSpaceRatio; }
+    bool operator==(const CompactionStrategy & rhs) const {
+        return _maxDeadBytesRatio == rhs._maxDeadBytesRatio &&
+            _maxDeadAddressSpaceRatio == rhs._maxDeadAddressSpaceRatio;
+    }
+    bool operator!=(const CompactionStrategy & rhs) const { return !(operator==(rhs)); }
+
+    static constexpr size_t DEAD_BYTES_SLACK = 0x10000u;
+
+    bool should_compact_memory(size_t used_bytes, size_t dead_bytes) const {
+        return ((dead_bytes >= DEAD_BYTES_SLACK) &&
+                (dead_bytes > used_bytes * getMaxDeadBytesRatio()));
+    }
+    
+    static constexpr size_t DEAD_ADDRESS_SPACE_SLACK = 0x10000u;
+    
+    bool should_compact_address_space(size_t used_address_space, size_t dead_address_space) const {
+        return ((dead_address_space >= DEAD_ADDRESS_SPACE_SLACK) &&
+                (dead_address_space > used_address_space * getMaxDeadAddressSpaceRatio()));
+    }
+};
+
+std::ostream& operator<<(std::ostream& os, const CompactionStrategy& compaction_strategy);
+
+}