Introduce DMA_BUF_IOCTL_RW_FILE ioctl for direct file I/O on dma-buf objects.
CURRENT WORKFLOW: 1. Allocate dma-buf: dmabuf_fd = dmabuf_alloc(len, heap_fd) 2. Map memory: vaddr = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, dmabuf_fd, 0) 3. File operations: file_fd = open(file_path, O_RDONLY) lseek(file_fd, pos) // 70% time spent on page cache management and memory copies read(file_fd, vaddr, len) KEY OPTIMIZATIONS: - Convert sg_table to bio_vec - Enable IOCB_DIRECT flag - Execute I/O via vfs_iocb_iter_read() OPTIMIZED WORKFLOW: dmabuf_fd = dmabuf_alloc(len, heap_fd) file_fd = open(file_path, O_RDONLY) if (direct_io) arg.flags |= DMA_BUF_RW_FLAGS_DIRECT ioctl(dmabuf_fd, DMA_BUF_IOCTL_RW_FILE, &arg) PERFORMANCE RESULTS: - Throughput: 3776 MB/s (UFS 4.0 4GB/s limit) - Page cache overhead eliminated - Direct data path reduces memory copies APPLICABLE SCENARIOS: - AI model loading - Real-time data acquisition - Task snapshot persistence
