International Business Machines Corporation

Phil C Yeh

Ronald Morton Smith, Sr

Eric M Schwarz

Shawn D Lundvall

Donald W Schmidt

Damian Leo Osisek

Lisa Cranton Heller

Patrick M West, Jr

Michael F Cowlishaw

Ronald M Smith

Jane Helen Bartik

Donald B Johnson

Stephen M Matyas

John D Wilkins

Peter Grimm Sutton

Dennis G Abraham

Robert S DeBellis

Julian Thomas

Jeffrey Mark Nick

An V Le

Wendell W Wilkinson

Rostislaw Prymak

Mark A Boonie

Michael James Kelly

Ramesh K Karne

Lucina L Green

Silvia Melitta Mueller

Camil Fayad

Randall J Easter

John K Li

Vincent A Spano

Edward J D'Avignon

An Van Le

Siegfried K H Sutter

Christian Jacobi

Chung-Lung K Shum

Gregory William Alexander

Bernd Nerz

David S Hutton

Roger E Hough

Michael Billeci

Klaus Meissner

Thomas J Dewkett

Jang-Soo Lee

Peter H Gum

Stephen J Schmandt

Rotislaw Prymak

Sandra L Rankin

Devon S Yu

Eric Mark Schwarz

Michael Frederic Cowlishaw

A central processing unit measurement facility is virtualized in order to support concurrent use of the facility by multiple guests executing within a virtual environment. Each guest of the environment has independent control over disablement/enablement of the facility for that guest.

Virtualization of a central processing unit measurement facility

A round-for-reround mode (preferably in a BID encoded Decimal format) of a floating point instruction prepares a result for later rounding to a variable number of digits by detecting that the least significant digit may be a 0, and if so changing it to 1 when the trailing digits are not all 0. A subsequent reround instruction is then able to round the result to any number of digits at least 2 fewer than the number of digits of the result. An optional embodiment saves a tag indicating the fact that the low order digit of the result is 0 or 5 if the trailing bits are non-zero in a tag field rather than modify the result. Another optional embodiment also saves a half-way-and-above indicator when the trailing digits represent a decimal with a most significant digit having a value of 5. An optional subsequent reround instruction is able to round the result to any number of digits fewer or equal to the number of digits of the result using the saved tags.

Round for reround mode in a decimal floating point instruction

A measurement sampling facility takes snapshots of the central processing unit (CPU) on which it is executing at specified sampling intervals to collect data relating to tasks executing on the CPU. The collected data is stored in a buffer, and at selected times, an interrupt is provided to remove data from the buffer to enable reuse thereof. The interrupt is not taken after each sample, but in sufficient time to remove the data and minimize data loss.

Managing a collection of data

The amount of host real storage provided to a large guest storage buffer is controlled. This control is transparent to the guest that owns the buffer and is executing an asynchronous process to update the buffer. The control uses one or more indicators to determine when additional host real storage is to be provided.

Virtualization of storage buffers used by asynchronous processes

Detection of whether a result of a floating point operation is safe. Characteristics of the result are examined to determine whether the result is safe or potentially unsafe, as defined by the user. An instruction is provided to facilitate detection of safe or potentially unsafe results.

Detection of potential need to use a larger data format in performing floating point operations

A decimal floating point finite number in a decimal floating point format is composed from the number in a different format. A decimal floating point format includes fields to hold information relating to the sign, exponent and significand of the decimal floating point finite number. Other decimal floating point data, including infinities and NaNs (not a number), are also composed. Decimal floating point data are also decomposed from the decimal floating point format to a different format. For composition and decomposition, one or more instructions may be employed, including a shift significand instruction.

Shift significand of decimal floating point data

A decimal floating point finite number in a decimal floating point format is composed from the number in a different format. A decimal floating point format includes fields to hold information relating to the sign, exponent and significand of the decimal floating point finite number. Other decimal floating point data, including infinities and NaNs (not a number), are also composed. Decimal floating point data are also decomposed from the decimal floating point format to a different format.

Decomposition of decimal floating point data

Growing community of inventors

Poughkeepsie, NY, United States of America

Phil C Yeh