intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 75 insertions, 0 deletions

diff --git a/util/system/direct_io.h b/util/system/direct_io.h
new file mode 100644
index 00000000000..6a3325a9608
--- /dev/null
+++ b/util/system/direct_io.h
@@ -0,0 +1,75 @@
+#pragma once
+
+#include "align.h"
+
+#include "file.h"
+#include <util/generic/buffer.h>
+
+// Supports Linux Direct-IO:
+// - Simple buffering logic.
+// - Default buffer size of 128KB matches VM page writeback granularity, to maximize IO throughput.
+// - Supports writing odd sized files by turning off direct IO for the last chunk.
+class TDirectIOBufferedFile {
+public:
+    TDirectIOBufferedFile(const TString& path, EOpenMode oMode, size_t buflen = 1 << 17);
+    ~TDirectIOBufferedFile();
+
+    void FlushData();
+    void Finish();
+    size_t Read(void* buffer, size_t byteCount);
+    void Write(const void* buffer, size_t byteCount);
+    size_t Pread(void* buffer, size_t byteCount, ui64 offset);
+    void Pwrite(const void* buffer, size_t byteCount, ui64 offset);
+
+    inline bool IsOpen() const {
+        return true;
+    }
+
+    inline ui64 GetWritePosition() const {
+        return WritePosition;
+    }
+
+    inline ui64 GetLength() const {
+        return FlushedBytes + DataLen;
+    }
+
+    inline FHANDLE GetHandle() {
+        return File.GetHandle();
+    }
+
+    inline void FallocateNoResize(ui64 length) {
+        File.FallocateNoResize(length);
+    }
+
+    inline void ShrinkToFit() {
+        File.ShrinkToFit();
+    }
+
+private:
+    inline bool IsAligned(i64 value) {
+        return Alignment ? value == AlignDown<i64>(value, Alignment) : true;
+    }
+
+    inline bool IsAligned(const void* value) {
+        return Alignment ? value == AlignDown(value, Alignment) : true;
+    }
+
+    size_t PreadSafe(void* buffer, size_t byteCount, ui64 offset);
+    size_t ReadFromFile(void* buffer, size_t byteCount, ui64 offset);
+    void WriteToFile(const void* buf, size_t len, ui64 position);
+    void WriteToBuffer(const void* buf, size_t len, ui64 position);
+    void SetDirectIO(bool value);
+
+private:
+    TFile File;
+    size_t Alignment;
+    size_t BufLen;
+    size_t DataLen;
+    void* Buffer;
+    TBuffer BufferStorage;
+    ui64 ReadPosition;
+    ui64 WritePosition;
+    ui64 FlushedBytes;
+    ui64 FlushedToDisk;
+    bool DirectIO;
+};