6947ch08.fm

Draft Document for Review April 7, 2004 6:15 pm

cryptographic processes that use SSL/TLS can be offloaded from the host to the PCICA feature to reduce CP and IFL usage, thus increasing system throughput.

Performance assists for Linux and z/VM

￿z990 adapter interruptions for Linux and z/VM - the z990, Linux on zSeries, and z/VM work together to provide performance improvements by exploiting extensions to the Queued Direct Input/Output (QDIO) architecture. Adapter interruptions, first added to z/Architecture with HiperSockets, provide an efficient, high-performance technique for I/O interruptions to reduce path lengths and overhead in both the host operating system and the adapter - FICON Express when using the FCP CHPID type, and OSA-Express when using the OSD CHPID type.

In extending the use of adapter interruptions to FCP and OSD (QDIO) channels, the programming overhead to process a traditional I/O interruption is reduced. This benefits OSA-Express TCP/IP support in both Linux on zSeries and z/VM, and FCP support in Linux on zSeries.

Adapter interruptions apply to a z990 FICON Express channel when in FCP mode (FCP CHPID type), which supports attachment of SCSI devices in a Linux on zSeries environment. This support is exclusive to z990 and applies to all of the OSA-Express features available on z990, when in QDIO mode (OSD CHPID type).

￿Performance assist for V=V guests in the z/VM environment - z990's support of virtual machine technology has been enhanced to include a new performance assist for virtualization of Adapter Interruptions. This new z990 performance assist is available to V=V guests (only pageable guests) that support QDIO (Queued Direct Input/Output) on z/VM V4.4 and later. The deployment of adapter interruptions improves efficiency and performance by reducing overhead.

The z990 performance assist for V=V guests is a passthrough architecture that reduces host programming overhead by avoiding the need to stop guest processing when adapter interruptions are presented. Without the assist, the z/VM control program must intercede to process and route the adapter interruptions.

The z990 performance assist improves Linux on zSeries performance under z/VM by allowing guest I/O - FICON (FCP CHPID type), HiperSockets (IQD CHPID type), and OSA-Express (OSD CHPID type) - to be handled with minimal z/VM overhead through direct presentation of adapter interruptions by the server to a pageable guest, boosting I/O performance.

8.8Capacity measurements

The result of all performance related characteristics of a server should be evaluated by their combined effect when estimating the system performance. Some design and/or implementation aspects can improve the performance of specific workloads and this should also be evaluated.

Measurements are the most accurate source for processor capacity data. Modeling techniques may produce reasonably accurate processor capacity data assuming all pertinent workload and hardware design and implementation factors are considered.

There is no reasonable way to construct a benchmark that simulates instruction paths and storage reference patterns typical of a production workload without using actual production software and activities.

222IBM eServer zSeries 990 Technical Guide

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IBM 990 manual Capacity measurements, Performance assists for Linux and z/VM
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990 specifications

The IBM 990 series, often referred to in the context of IBM's pioneering efforts in the realm of mainframe computing, represents a unique chapter in the history of information technology. Introduced in the late 1960s, the IBM 990 series was designed as a powerful tool for enterprise-level data processing and scientific calculations, showcasing the company's commitment to advancing computing capabilities.

One of the main features of the IBM 990 was its architecture, which was built to support a wide range of applications, from business processing to complex scientific computations. The system employed a 32-bit word length, which was advanced for its time, allowing for more flexible and efficient data handling. CPUs in the IBM 990 series supported multiple instructions per cycle, which contributed significantly to the overall efficiency and processing power of the machines.

The technology behind the IBM 990 was also notable for its use of solid-state technology. This provided a shift away from vacuum tube systems that were prevalent in earlier computing systems, enhancing the reliability and longevity of the hardware. The IBM 990 series utilized core memory, which was faster and more reliable than the magnetic drum memory systems that had been standard up to that point.

Another defining characteristic of the IBM 990 was its extensibility. Organizations could configure the machine to suit their specific needs by adding memory, storage, and peripheral devices as required. This modular approach facilitated the growth of systems alongside the technological and operational demands of the business environments they served.

In terms of software, the IBM 990 series was compatible with a variety of operating systems and programming environments, including FORTRAN and COBOL, enabling users to access a broader array of applications. This versatility was a significant advantage, making the IBM 990 an appealing choice for educational institutions, research facilities, and enterprises alike.

Moreover, the IBM 990 was engineered to support multiprocessing, which allowed multiple processes to run simultaneously, further increasing its effectiveness in tackling complex computing tasks.

In summary, the IBM 990 series represents a significant advancement in computing technology during the late 20th century. With a robust architecture, versatile configuration options, and a focus on solid-state technology, the IBM 990 facilitated substantial improvements in data processing capabilities, making it a cornerstone for many businesses and academic institutions of its time. Its impact can still be seen today in the continued evolution of mainframe computing.
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