SPEC CPU2006 Platform Settings for Intel-based systems

Commands and Options Used to Submit Benchmark Runs

submit= MYMASK=`printf '0x%x' $((1<<$SPECCOPYNUM))`; /usr/bin/taskset $MYMASK $command

When running multiple copies of benchmarks, the SPEC config file feature submit is sometimes used to cause individual jobs to be bound to specific processors. This specific submit command is used for Linux. The description of the elements of the command are:

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 affect 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'

submit= $[top]/mysubmit.pl $SPECCOPYNUM "$command"

On Xeon 74xx series processors, some benchmarks at peak will run n/2 copies on a system with n logical processors. The mysubmit.pl script assigns each copy in such a way that no two copies will share an L2 cache, for optimal performance. The script looks in /proc/cpuinfo to come up with the list of cores that will satisfy this requirement. The source code is shown below.

Source ******************************************************************************************************


#!/usr/bin/perl
 
use strict;
use Cwd;
 
# The order in which we want copies to be bound to cores
# Copies: 0, 1, 2, 3
# Cores:  0, 1, 3, 6
 
my $rundir        = getcwd;
 
my $copynum = shift @ARGV;

my $i;
my $j;
my $tag;
my $num;
my $core;
my $numofcores; 

my @proc;
my @cores;

open(INPUT, "/proc/cpuinfo") or
   die "can't open /proc/cpuinfo\n"; 

#open(OUTPUT, "STDOUT");

# proc[i][0] = logical processor ID
# proc[i][1] = physical processor ID
# proc[i][2] = core ID

$i = 0;
$numofcores = 0;

while(<INPUT>)
{
  chop;
 
  ($tag, $num) = split(/\s+:\s+/, $_);


  if ($tag eq "processor") {
      $proc[$i][0] = $num;
  }

  if ($tag eq "physical id") {
      $proc[$i][1] = $num;
  }

  if ($tag eq "core id") {
      $proc[$i][2] = $num;
      $i++;
      $numofcores++;
  }
}

$i = 0;
$j = 0;

for $core (0, 4, 2, 1, 5, 3) {
  while ($i < $numofcores) {
     if ($proc[$i][2] == $core) {
        $cores[$j] = $proc[$i][0];
        $j++;
     }
     $i++;
  }
  $i=0;
}

open  RUNCOMMAND, "> runcommand" or die "failed to create run file";
print RUNCOMMAND "cd $rundir\n";
print RUNCOMMAND "@ARGV\n";
close RUNCOMMAND;
system 'taskset', '-c', $cores[$copynum], 'sh', "$rundir/runcommand";


Shell, Environment, and Other Software Settings

HUGETLB_MORECORE
Set this environment variable to "yes" to enable applications to use large pages.
LD_PRELOAD=/usr/lib64/libhugetlbfs.so
Setting this environment variable is necessary to enable applications to use large pages.
KMP_STACKSIZE
Specify stack size to be allocated for each thread.
KMP_AFFINITY
OMP_NUM_THREADS
Sets the maximum number of threads to use for OpenMP* parallel regions if no other value is specified in the application. This environment variable applies to both -openmp and -parallel (Linux and Mac OS X) or /Qopenmp and /Qparallel (Windows). Example syntax on a Linux system with 8 cores: export OMP_NUM_THREADS=8
ulimit -s <n>
Sets the stack size to n kbytes, or unlimited to allow the stack size to grow without limit.

Operating System Tuning Parameters

echo 1 > /proc/sys/vm/drop_caches
Writing to this will cause the kernel to free pagechace

autoup= (Unix /etc/system)
When the file system flush daemon fsflush runs, it writes to disk all modified file buffers that are more than n seconds old.

psrset -c (Unix, superuser commands)
Creates a new processor set and displays the new processor set ID.

psrset -e (Unix, superuser commands)
Executes a command (with optional arguments) in the specified processor set. The command process and any child processes are executed only by processors in the processor set.

tune_t_fsflushr= (Unix /etc/system)
Controls the number of seconds between runs of the file system flush daemon, fsflush.


Firmware / BIOS / Microcode Settings

Hardware Prefetch:
This BIOS option allows the enabling/disabling of a processor mechanism to prefetch data into the cache according to a pattern-recognition algorithm In some cases, setting this option to Disabled may improve performance. Users should only disable this option after performing application benchmarking to verify improved performance in their environment.
Adjacent Sector Prefetch:
This BIOS option allows the enabling/disabling of a processor mechanism to fetch the adjacent cache line within a 128-byte sector that contains the data needed due to a cache line miss. In some cases, setting this option to Disabled may improve performance. Users should only disable this option after performing application benchmarking to verify improved performance in their environment.
Adjacent Cache Line Prefetch:
This BIOS option allows the enabling/disabling of a processor mechanism to fetch the adjacent cache line within a 128-byte sector that contains the data needed due to a cache line miss. In some cases, setting this option to Disabled may improve performance. Users should only disable this option after performing application benchmarking to verify improved performance in their environment.
L1 Data Prefetch: Enabled:
This BIOS option allows the enabling/disabling L1 cache Data prefetch.
C-State : Disabled
Enable/Disable CPUs to enter C-State (lower power CPU state) while the system is idle. This helps to lower power consumption when enabled.
Data Reuse Optimization : Disabled
Enabling this BIOS option reduces the frequency of L3 cache updates from L1. This may improve performance by reducing the internal bandwidth consumed by constantly updating L1 cache lines in L3. Since this results in more fetches to main memory, setting this option to Disabled may improve performance in some cases. Users should only disable this option after performing application benchmarking to verify improved performance in their environment.