System method and apparatus for efficiently transferring datastream in multimedia system

Abstract

A general purpose interface is provided to a file system of a multimedia server for improving datastream throughput by avoiding data copying and context switching. The file system includes an export registration service providing function pointers to the file system's implementation of a predefined set of zero copy interfaces. These interfaces include an initialization service to set up necessary data structures and to place use counts on objects to prevent them from being removed while zero copy operations are in progress. A termination service in the zero copy interfaces cleans up data structures and removes use counts. Additional services validate that a specified file is suitable for zero copy operations, find and record file attributes needed to later acquire buffers at interrupt level. A data structure is defined to hold these attributes for subsequent calls. Another service locks a buffer at an interrupt level and returns the amount of data present, and provides addressability to the buffer in another address space context. A data structure holds these buffer attributes for subsequent calls. A service is additionally provided to unlock the buffer at interrupt level. Finally, a service provides information on changes to the access pattern of the file such as would be needed to support VCR functions. A hash chain emplyoing a singly linked list updated atomically allows for safe buffer lookups at interrupt level. Compare-and-swap locking faciliates this. A mailbox interface useful at interrupt leve provides prefetch and release information to the daemon. In case of a lock collision or where the buffer is not available, the buffer is acquired in a process context. <IMAGE>

Description

technical field [0001] This invention relates to computerized multimedia servers, and more particularly to techniques for efficiently transferring data streams between devices in such systems, such as from a disk storage subsystem to a network or video decoding card. Background technique [0002] Multimedia systems typically involve large numbers of data streams representing high-density multimedia data that must be transferred through the system with very high efficiency. A representative example is the "Video on Demand" service system. Various methods have been investigated in an attempt to efficiently move data through these systems. Many of these systems use the well-known Unix operating system or its derivatives as their operating system, as is commonly seen in client server environments that implement multimedia content delivery systems. A serious deficiency inherent in such Unix-based systems is that the mechanisms employed to transfer data therein do not optimize e...

AI Technical Summary

Problems solved by technology

A serious deficiency inherent in such Unix-based systems is that the mechanisms employed to transfer data therein do not optimize efficiency as desired in systems involving very complex multimedia data streams

However, this approach is quite problematic in relation to the reasons for fetching data into shared memory in the first place, such as for just-in-time data management to provide data transfer while avoiding copying the data and only using the corresponding CPU overhead. efficient mechanism

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