2006 USENIX Annual Technical Conference Abstract
Pp. 143–156 of the Proceedings
Understanding and Addressing Blocking-Induced Network Server Latency
Yaoping Ruan, IBM T.J. Watson Research Center; Vivek Pai, Princeton University
Abstract
We investigate the origin and components of network server latency
under various loads and find that filesystem-related kernel queues
exhibit head-of-line blocking, which leads to bursty
behavior in event delivery and process scheduling. In turn, these
problems degrade the existing fairness and scheduling policies in the
operating system, causing requests
that could have been served in memory, with low latency, to
unnecessarily wait on disk-bound requests. While this batching
behavior only mildly affects throughput, it severely degrades latency.
This problem manifests itself in fairness and
service quality degradation, a phenomenon we call service
inversion.
We show a portable solution that avoids these problems without kernel or
filesystem modifications, We modify two different Web servers to use
this approach, and demonstrate a qualitatively different change in
their latency profiles, generating more than an order of magnitude
reduction in latency. The resulting
systems are able to serve most requests without being tied to disk
performance, and they scale better with improvements in processor
speed. These results are not dependent on server software
architecture, and can be profitably applied to experimental and
production servers.
- View the full text of this paper in HTML and PDF. Listen to the presentation in MP3 format.
Until June 2007, you will need your USENIX membership identification in order to access the full papers. The Proceedings are published as a collective work, © 2006 by the USENIX Association. All Rights Reserved. Rights to individual papers remain with the author or the author's employer. Permission is granted for the noncommercial reproduction of the complete work for educational or research purposes. USENIX acknowledges all trademarks within this paper.
- If you need the latest Adobe Acrobat Reader, you can download it from Adobe's site.
|
