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cleanup and shred multi-armed bandit

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This commit is contained in:
Hendrik Schutter
2026-05-02 12:25:21 +02:00
parent 716ab5614f
commit 05a3750b03
6 changed files with 113 additions and 99 deletions
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include/shred.h
+27 -29
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@@ -18,26 +18,22 @@
#include <string.h>
#include <chrono>
// Adaptive chunk size optimization - uncomment to enable
#define ADAPTIVE_CHUNK_SIZE
// Adaptive chunk size optimization with multi-armed bandit - always enabled
// Chunk size configuration
#define CHUNK_SIZE_START 1024 * 1024 * 32 // Starting chunk size: 32MB
#define CHUNK_SIZE_MIN 1024 * 1024 * 4 // Minimum chunk size: 4MB
#define CHUNK_SIZE_MAX 1024 * 1024 * 128 // Maximum chunk size: 128MB
#define CHUNK_SIZE_STEP_UP 1024 * 1024 * 2 // Increase step: 2MB
#define CHUNK_SIZE_STEP_DOWN 1024 * 1024 * 4 // Decrease step: 4MB
#define CHUNK_MEASURE_INTERVAL 64 // Measure performance every 64 chunks
#define CHUNK_SIZE_START 1024 * 1024 * 32 // Starting chunk size: 32MB
#define CHUNK_SIZE_MIN 1024 * 1024 * 16 // Minimum chunk size: 16MB (increased from 4MB to prevent premature convergence)
#define CHUNK_SIZE_MAX 1024 * 1024 * 128 // Maximum chunk size: 128MB
#define CHUNK_SIZE_STEP_UP 1024 * 1024 * 4 // Increase step: 4MB (symmetric with step down)
#define CHUNK_SIZE_STEP_DOWN 1024 * 1024 * 4 // Decrease step: 4MB (symmetric exploration)
#define CHUNK_MEASURE_INTERVAL 64 // Measure performance every 64 chunks
#ifdef ADAPTIVE_CHUNK_SIZE
// Use max buffer size when adaptive mode is enabled
// Multi-armed bandit exploration parameters
#define EXPLORATION_EPSILON 0.10 // 10% exploration rate (epsilon-greedy)
#define REEXPLORATION_INTERVAL 500 // Force re-exploration every 500 chunks
// Buffer sizes - always use maximum for adaptive mode
#define CHUNK_SIZE CHUNK_SIZE_MAX
#define TFNG_DATA_SIZE CHUNK_SIZE_MAX
#else
// Use fixed chunk size when adaptive mode is disabled
#define CHUNK_SIZE CHUNK_SIZE_START
#define TFNG_DATA_SIZE CHUNK_SIZE
#endif
// #define DEMO_DRIVE_SIZE 1024*1024*256L // 256MB
// #define DEMO_DRIVE_SIZE 1024*1024*1024L // 1GB
@@ -52,47 +48,49 @@ protected:
public:
Shred();
~Shred();
int shredDrive(Drive* drive, int* ipSignalFd);
int shredDrive(Drive *drive, int *ipSignalFd);
private:
fileDescriptor randomSrcFileDiscr;
fileDescriptor driveFileDiscr;
#ifdef ADAPTIVE_CHUNK_SIZE
unsigned char* caTfngData; // Dynamic buffer allocation for adaptive mode
unsigned char* caReadBuffer; // Dynamic buffer allocation for adaptive mode
#else
unsigned char caTfngData[TFNG_DATA_SIZE];
unsigned char caReadBuffer[CHUNK_SIZE];
#endif
unsigned char *caTfngData;
unsigned char *caReadBuffer;
unsigned long ulDriveByteSize;
unsigned long ulDriveByteOverallCount = 0; // all bytes shredded in all iterations + checking -> used for progress calculation
double d32Percent = 0.0;
double d32TmpPercent = 0.0;
#ifdef ADAPTIVE_CHUNK_SIZE
// Adaptive chunk size optimization members
size_t currentChunkSize;
size_t bestChunkSize;
unsigned int chunkCounter;
unsigned int totalChunkCounter; // Total chunks written (for periodic re-exploration)
std::chrono::high_resolution_clock::time_point measurementStartTime;
double bestThroughputMBps;
double lastThroughputMBps;
unsigned long bytesWrittenInMeasurement;
bool throughputIncreasing;
// Multi-armed bandit exploration state
bool explorationMode; // Currently in exploration mode?
size_t explorationChunkSize; // Chunk size being tested during exploration
// Adaptive methods
void startMeasurement();
void evaluateThroughput(Drive* drive);
void adjustChunkSize(Drive* drive);
void evaluateThroughput(Drive *drive);
void adjustChunkSize(Drive *drive);
size_t getCurrentChunkSize() const;
#endif
// Multi-armed bandit methods
bool shouldExplore(); // Decide: explore or exploit?
void performExploration(Drive *drive); // Execute exploration phase
inline double calcProgress();
int iRewindDrive(fileDescriptor file);
long getDriveSizeInBytes(fileDescriptor file);
unsigned int uiCalcChecksum(fileDescriptor file, Drive* drive, int* ipSignalFd);
unsigned int uiCalcChecksum(fileDescriptor file, Drive *drive, int *ipSignalFd);
void cleanup();
};