Platform settings file

System and Other Tuning Information

One or more of the following settings may have been set. If so, the "Platform Notes" section of the report will say so; and you can read below to find out more about what these settings mean.

PowerNow (Default = Enabled):

This feature Enables/Disables the PowerNow feature of the processor

Fan Speed Control Mode: (Default = Balanced / BL)

This feature allows the user to select the fan cooling solution for the system. Values for this BIOS option can be:

• Full Speed/FS: Provides the maximum efficient solution by configuring fan speeds to the maximum required to provide adequate cooling.
• Performance/PF: Provides the better efficient solution by configuring fan speeds to the better required to provide adequate cooling.
• Balanced/BL: Provides the balanced efficient solution by configuring fan speeds to the balanced required to provide adequate cooling and Energy Saving.
• Energy Saving/ES : Provides the lower power and lower Noise

Linux Huge Page settings

In order to take full advantage of using x86 Open64's huge page runtime library, your system must be configured to use huge pages. It is safe to run binaries compiled with "-HP" on systems not configured to use huge pages, however, you will not benefit from the performance improvements huge pages offer. To configure your system for huge pages perform the following steps:

• Create a mount point for the huge pages: "mkdir /mnt/hugepages"
• The huge page file system needs to be mounted when the systems reboots. Add the following to a system boot configuration file before any services are started: "mount -t hugetlbfs nodev /mnt/hugepages"
• Set vm/nr_hugepages=N in your /etc/sysctl.conf file where N is the maximum number of pages the system may allocate.
• Reboot to have the changes take effect.

Note that further information about huge pages may be found in your Linux documentation file: /usr/src/linux/Documentation/vm/hugetlbpage.txt

Transparent Huge Pages

The use of transparent huge pages is a feature of some newer Linux distributions which allows huge pages to be allocated and de-allocated automatically without hugetlbfs configuration.

On RHEL 6, the default is to have them enabled. To disable the use of transparent huge pages, do the following:

• Set transparent_hugepage=never in your /boot/grub/menu.lst file
• Reboot to have the changes take effect.

HUGETLB_LIMIT

For the x86 Open64 compiler, the maximum number of huge pages an application is allowed to use can be set at run time via the environment variable HUGETLB_LIMIT. If not set, then the process may use all available huge pages when compiled with "-HP (or -HUGEPAGE)" or a maximum of n pages where the value of n is set via the compile time flag "-HP:limit=n".

randomize_va_space

This option can be used to select the type of process address space randomization that is used in the system, for architectures that support this feature.

• 0 - Turn the process address space randomization off. This is the default for architectures that do not support this feature anyways, and kernels that are booted with the "norandmaps" parameter.
• 1 - Make the addresses of mmap base, stack and VDSO page randomized.
• 2 - Additionally enable heap randomization.

The default varies among distributions. To disable the use address space randomization, do the following:

• Set kernel/randomize_va_space=0 in your /etc/sysctl.conf file
• Reboot to have the changes take effect.

Using numactl to bind processes and memory to cores

For multi-copy runs or single copy runs on systems with multiple sockets, it is advantageous to bind a process to a particular core. Otherwise, the OS may arbitrarily move your process from one core to another. This can effect performance. To help, SPEC allows the use of a "submit" command where users can specify a utility to use to bind processes. We have found the utility 'numactl' to be the best choice.

numactl runs processes with a specific NUMA scheduling or memory placement policy. The policy is set for a command and inherited by all of its children. The numactl flag "--physcpubind" specifies which core(s) to bind the process. "-l" instructs numactl to keep a process memory on the local node while "-m" specifies which node(s) to place a process memory. For full details on using numactl, please refer to your Linux documentation, 'man numactl'

Note that some versions of numactl, particularly the version found on SLES 10, we have found that the utility incorrectly interprets application arguments as it's own. For example, with the command "numactl --physcpubind=0 -l a.out -m a", numactl will interpret a.out's "-m" option as it's own "-m" option. To work around this problem, a user can put the command to be run in a shell script and then run the shell script using numactl. For example: "echo 'a.out -m a' > run.sh ; numactl --physcpubind=0 bash run.sh"

ulimit -s <n>

Sets the stack size to n kbytes, or unlimited to allow the stack size to grow without limit.

ulimit -l <n>

Sets the maximum size of memory that may be locked into physical memory.

OMP_NUM_THREADS

Sets the maximum number of OpenMP parallel threads auto-parallelized (-apo) applications may use.

O64_OMP_AFFINITY_MAP

Specifies the thread-CPU relationship when the operating system's affinity mechanism is used to assign OpenMP threads to CPUs.

O64_OMP_SPIN_USER_LOCK

Specifies whether or not to use the user-level spin mechanism for OpenMP locks. If the variable is set to TRUE then user-level spin mechanisms are used. If the variable is set to FALSE then pthread mutexes are used. The default if the variable is not set is the same as FALSE.

powersave -f (on SuSE)

Makes the powersave daemon set the CPUs to the highest supported frequency.

/etc/init.d/cpuspeed stop (on Red Hat)

Disables the cpu frequency scaling program in order to set the CPUs to the highest supported frequency.

LD_LIBRARY_PATH

An environment variable set to include the x86 Open64 and SmartHeap libraries used during compilation of the binaries. This environment variable setting is not needed when building the binaries on the system under test.