SCO UnixWare 2.1 Technical Summary - Bandwidthco Computer ...

An SCO Technical White Paper Version 2.1.2
SCO UnixWare 2.1 Symmetrical Multi-Processing and Threads
As mentioned above, the SCO UnixWare 2.1 kernel was designed and developed as a multiprocessor
system at a time when multi-processing technology is becoming remarkably more
powerful, yet less expensive (especially on Intel architectures) Working closely with Intel
Corporation and other SMP pioneers, engineers from USL and Novell developed a kernel that is
portable and flexible enough to quickly support emerging next-generation SMP server
architectures from a number of leading companies. The result was the SVR4.2MP kernel, the
basis for SCO UnixWare 2.1. The product of a long development and testing process, the SCO
UnixWare 2.1 kernel was designed to maximize performance and scalability in SMP servers.
Since it’s release, SCO UnixWare 2.1 has garnered many performance benchmark records and
accolades from press and analysts.
SMP-based systems are very flexible and have the potential to minimize processor bottlenecks
and allow maximum system efficiency. The SCO UnixWare 2.1 kernel is designed to take
advantage of any multiprocessing hardware design using the Intel architecture. Key
technologies that make the SCO UnixWare 2 kernel so outstanding include:
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• Re-entrant code to enable multiple processors to run without affecting the state of other
execution contexts.
• Fine-grained locks to protect critical data from simultaneous modification.
• Fully pre-emptable kernel allows processes of a higher priority pre-empt any kernel
process of a lower priority. The degree of pre-emption in the kernel improves the
average process performance of the overall system and of threaded applications in
specific (like databases).
• Multithreading of all major kernel components to optimize performance.
• User-level threads - the inclusion of user-level threads allows SCO engineers to make
more components of the operating system SMP-aware. It also allows application
developers access to the performance improvements o be gained from taking advantage
of SMP capabilities.
• Lightweight Processes - a finer gradation of addressable process entities that allow
parallel aspects of a single process to be executed simultaneously.
• Memory-mapped files are an efficient, transparent way to transfer data from memory
to files. This is especially valuable when dealing with large files.
• Flexible scheduling mechanisms to support scheduling and load balancing across
different processors.
• Virtual memory management enhancements to handle multiprocessing, LWPs, and
large databases.
• Processor cache affinity based scheduling - provides a highly efficient means of
scheduling processes in and out of multiple CPUs.
• Auto configuration and dynamic loading for device drivers allows portions of the
kernel to be loaded, services and then reloaded without having to rebuild the kernel or
shut the machine down.
SCO UnixWare 2.1 Device Driver Support
SCO UnixWare 2.1 provides three device driver interfaces, all of which are based on a single
specification, the Device Driver Interface/Device Kernel Interface (DDI/DKI). The DDI/DKI is a
set of kernel level interfaces designed to reduce the cost of releasing drivers by providing source
and binary compatibility guarantees. In addition to the traditional block and character device
driver interfaces, and the STREAMS interface introduced to support network device drivers,
SCO UnixWare 2.1 provides the Portable Device Interface (PDI) for the support of storage
device drivers.