Began re-architecting the project for concurrency support

The project is now in a state where it builds, but it probably has a lot
of bugs still.

1 files changed, 76 insertions, 0 deletions

diff --git a/include/framework/Scheduler.h b/include/framework/Scheduler.h
new file mode 100644
index 0000000..cd3f430
--- /dev/null
+++ b/include/framework/Scheduler.h
@@ -0,0 +1,76 @@
+/*
+ * include/framework/Scheduler.h
+ *
+ * Copyright (C) 2023 Douglas Rumbaugh <drumbaugh@psu.edu> 
+ *                    Dong Xie <dongx@psu.edu>
+ *
+ * All rights reserved. Published under the Modified BSD License.
+ *
+ */
+#pragma once
+
+#include <vector>
+#include <memory>
+#include <queue>
+
+#include "util/types.h"
+#include "framework/ShardInterface.h"
+#include "framework/QueryInterface.h"
+#include "framework/RecordInterface.h"
+#include "framework/MutableBuffer.h"
+#include "framework/Configuration.h"
+#include "framework/ExtensionStructure.h"
+
+namespace de {
+
+
+struct MergeTask {
+    level_index m_source_level;
+    level_index m_target_level;
+    size_t m_size;
+    size_t m_timestamp;
+
+    bool operator<(MergeTask &other) {
+        return m_timestamp < other.m_timestamp;
+    }
+};
+
+
+template <RecordInterface R, ShardInterface S, QueryInterface Q, LayoutPolicy L>
+class Scheduler {
+    typedef ExtensionStructure<R, S, Q, L> Structure;
+public:
+    /*
+     * Memory budget stated in bytes, with 0 meaning unlimited. Likewise, 0 threads means 
+     * unlimited.
+     */
+    Scheduler(size_t memory_budget, size_t thread_cnt) 
+        : m_memory_budget((memory_budget) ? memory_budget : UINT64_MAX)
+        , m_thread_cnt((thread_cnt) ? thread_cnt : UINT64_MAX)
+        , m_used_memory(0)
+        , m_used_threads(0)
+    {}
+
+    bool schedule_merge(Structure *version, MutableBuffer<R> *buffer) {
+        // FIXME: this is a non-concurrent implementation
+        return version->merge_buffer(buffer);
+    }
+
+private:
+    size_t get_timestamp() {
+        auto ts = m_timestamp.fetch_add(1);
+        return ts;
+    }
+
+    size_t m_memory_budget;
+    size_t m_thread_cnt;
+
+    alignas(64) std::atomic<size_t> m_used_memory;
+    alignas(64) std::atomic<size_t> m_used_threads;
+    alignas(64) std::atomic<size_t> m_timestamp;
+
+    std::priority_queue<MergeTask> m_merge_queue;
+    std::mutex m_merge_queue_lock;
+};
+
+}