Finding Speed Bumps: Web Server Performance Analysis and Anomaly Detection via Wide-Spectrum Microbenchmarking

Abstract:

We investigate the use of parameterized mi- crobenchmarks to explore Web
server perfor- mance over a wider range of workloads than is tra-
ditionally represented in “realistic” benchmarks. We find that these
“wide-spectrum” tests not only give insights into the strengths and
weaknesses of various server software, but also reveal long- standing
performance problems that have either been undiscovered or improperly
diagnosed. To enable our approach, we have developed “Flexi- client”, a
componentized testing system that al- lows the easy creation of
parameterized workload generators to test HTTP-based servers.

Even with simple static file workloads, we un- cover a number of
performance problems on both popular and experimental systems, including
the following: severe deterioration of FreeBSD’s min- core system call
performance with growing mem- ory size on event-driven servers, process
sched- uler overhead crippling persistent connection ben- efits for Apache
on Linux, and low multiproces- sor performance gains on Linux. We
addition- ally discover some other interesting behaviors that run counter
to conventional wisdom: the most popular web server benchmark software
generates surprisingly small working sets, and select-based servers may
not suffer as much from idle persis- tent connections as previously
assumed.