Performance Analysis and Optimization of the Hurricane File System ...

CHAPTER 1. INTRODUCTION AND MOTIVATION 3
kernel. It relies on memory-mapped input/output (I/O) capabilities of the memory management system to
perform efficient data transfers between disks and requesting applications.
HFS contains the flexibility that is necessary to match the goals of K42, which is why it was selected
as the K42 native file system. However, the scalability characteristics of HFS were, to date, never really
tested 2 . A secondary motivation is to evaluate the effectiveness and robustness of the original file system
design on new operating system and hardware technology, which has evolved significantly since the inception
of Hector and Hurricane. That is, we can now determine whether the initial design withstands the test of
time and can exploit new technologies, or whether the design is restricted to exploiting only “technology
of moment”. Since K42 is the University of Toronto’s third generation research operating system, many
bottlenecks that were present in the previous generations have been eliminated or reduced 3 . K42 is a faster
operating system that can stress a file system to an extent not possible in the past. As well, the disparity
between processor and memory speeds has become more severe, possibly affecting file system performance.
A good design would nullify the disparity.
1.3 K42 Operating System
K42 is a research operating system currently being developed to address performance and scalability issues
of system software on large-scale, shared-memory, NUMA multiprocessor computers. The operating system
is a product of research at the University of Toronto in collaboration with the K42 group at the IBM Thomas
J. Watson Research Center. The core of K42 is based on the University of Toronto’s Tornado Operating
System [22]. K42 is the university’s third generation of research on scalable operating systems. Hurricane
OS / Hector Multiprocessor was the first generation and Tornado OS / NUMAchine Multiprocessor [24] was
the second generation. K42 runs on 64-bit processors that include the 64-bit PowerPC, MIPS, and AMD
x86-64 processors. In terms of complete systems, K42 runs on SimOS machine simulation software [62]
(under 64-bit PowerPC and MIPS emulation), the NUMAchine multiprocessor (MIPS), and IBM RS/6000
64-bit PowerPC computers.
K42 uses a micro-kernel architecture rather than the traditional monolithic kernel design. K42 consists of
a small exception-handling component that serves as the micro-kernel, a fast IPC mechanism, and servers for
all other components of the operating system. These servers exist in separate address spaces and rely upon the
fast IPC mechanism for communication with the micro-kernel and other servers. Examples of fundamental
servers include the memory management system and processor scheduler. Other servers include the resource
and may be used interchangeably.
2As described by Krieger in [34, p. 72], the scalability of HFS was not fully explored under the original Hector / Hurricane
environment.
3Improvements were achieved mainly between Hurricane and Tornado operating systems. Some of these improvements
include IPC performance, the elimination of hierarchical clustering and promotion of clustered objects, and simpler finer grain
locking.