PipeBWrite: Shortening the Buffered Write Critical Path with Deferred Non-Critical Steps

Buffered I/O is the dominant storage interface, but its synchronous and monolithic write path limits performance for write-intensive applications. Prior work either applies narrow optimizations to individual steps of the write path or adopts asynchronous designs that require application changes.

In this paper, we present PipeBWrite, a transparent buffered write scheme that retains the synchronous interface while extracting the performance benefits of asynchronous execution. Based on data dependency analysis, PipeBWrite decomposes buffered writes into a two-stage pipeline: the foreground thread performs only the critical data copy needed for immediate user-buffer reuse, while non-critical kernel bookkeeping is offloaded to background threads. To ensure correctness, PipeBWrite introduces a lightweight inter-request visibility tracker that preserves POSIX semantics despite decoupled execution. It also employs holistic optimizations, including adaptive allocation, inline zeroing, and request batching, to minimize coordination overhead. PipeBWrite is implemented in the Linux Virtual File System layer and requires no application changes. Across four applications with the ext4 and XFS filesystems, PipeBWrite improves throughput by up to 25% for RocksDB and 21% for Kafka over vanilla Linux and StreamCache. For FIO synthetic workloads, it achieves up to 2.34× higher throughput and reduces write latency by up to 58%.