Linux And System Libraries; Introduction; Linux Operating System-Specific Optimizations - IBM Power7 Optimization And Tuning Manual

5.1 Linux and system libraries

This section contains information about Linux and system libraries.

5.1.1 Introduction

When you work with IBM POWER7 processor-based servers, systems, and solutions, a solid
choice for running enterprise-level workloads is Linux. Red Hat Enterprise Linux (RHEL) and
SUSE Linux Enterprise Server (SLES) provide operating systems that are optimized and
targeted for the Power Architecture. These operating systems run natively on the Power
Architecture and are designed to take full advantage of the specialized features of
Power Systems.
Both RHEL and SLES provide the tools, kernel support, optimized compilers, and tuned
libraries for POWER7 Systems. The Linux distributions provide for excellent performance,
and more application and customer-specific tuning approaches are available. IBM provides a
number of value-add packages, tools, and extensions that provide for more tunings,
optimizations, and products for the best possible performance on POWER7. The typical Linux
open source performance tools that Linux users are comfortable with are available on the
PowerLinux systems.
The Linux distributions are enabled to run on small Power Micro-Partitioning partitions
through the broad range of IBM Power offerings, from low-cost PowerLinux servers and Flex
System nodes, up through the largest IBM Power 770 and Power 795 servers.
IBM premier products, such as IBM XL compilers, IBM Java products, IBM WebSphere, and
IBM DB2 database products, all provide Power optimized support with the RHEL and SUSE
operating systems.
For more information about this topic, see 5.2, "Related publications" on page 106.

5.1.2 Linux operating system-specific optimizations

This section describes optimization methods specific to Linux.
GCC, toolchain, and IBM Advance Toolchain
This section describes 32-bit and 64-bit modes and CPU-tuned libraries.
Linux support for 32-bit and 64-bit modes
The compiler and runtime are fully capable of supporting either 32-bit or 64-bit mode
applications simultaneously. The compilers can select the target mode through the -m32 or
-m64 compiler options.
For the SUSE Linux Enterprise Server and Red Hat Enterprise Linux distributions, the shared
libraries have both 32-bit and 64-bit versions. The toolchain (compiler, assembler, linker, and
dynamic linker) selects the correct libraries based on the -ms32 or -m64 option or the mode of
the application program.
The Advance Toolchain defaults to 64-bit, as do SLES 11 and RHEL 6. Older distribution
compilers defaulted to 32-bit.
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