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<title>SPEC CPU2006 Software OS and BIOS tuning Descriptions NEC Intel-based systems
applications</title>
<header>
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 Copyright &copy; 2007 Intel Corporation.  All Rights Reserved.</p>
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</header>

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  Explanations of platform info, such as BIOS settings
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<platform_settings>
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<p><b>Platform settings</b></p>

<p>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.</p>


<p><b>Adjacent Cache Line Prefetch:</b></p> 
<p>
       This BIOS option allows the enabling/disabling of a processor mechanism to                 
       fetch the adjacent cache line within an 128-byte sector that contains 
       the data needed due to a cache line miss. </p>
<p>                
       In some limited cases, setting this option to Disabled may improve
       performance. In the majority of cases, the default value of Enabled                        
       provides better performance.  Users should only disable this option 
       after performing application benchmarking to verify improved
       performance in their environment.</p>

<p><b>Hardware Prefetcher:</b></p> 
<p>
       This BIOS option allows allows the enabling/disabling of a processor 
       mechanism to prefetch data into the cache according to a pattern 
       recognition algorithm.</p>
<p>                
       In some limited cases, setting this option to Disabled may improve
       performance. In the majority of cases, the default value of Enabled 
       provides better performance.  Users should only disable this option 
       after performing application benchmarking to verify improved
       performance in their environment.</p>

 <p><b>FSB High Bandwidth Optimization:</b></p> 
	 <p>
	 Enabling this option allows the chipset to defer memory transactions and process them out of order for optimal performance. 
	 </p>

<p><b>Intel SpeedStep Technology:</b></p> 
<p>
       This BIOS option allows the system to dynamically adjust 
       processorvoltage and core frequency, which results in decreased power 
       consumption, which results in decreased heat production, which in turn allows 
       improved acoustics because fans do not need to spin as quickly. </p>

<p><b>NUMA configuration:</b></p> 
<p>
       This BIOS setting when set to NUMA (Non-Uniform Memory Access) configures the system
       memory into blocks local to each processor.
       A NUMA-aware operating system can use this configuration to intelligently allocate
       memory for optimal performance.</p>

<p><b>Hyper-Threading Technorogy:</b></p> 
<p>
       This BIOS setting disables/enables Hyper-Threading (HT) Technology. 
       HT enables the processor to allocate an additional thread to a core.</p>


<p><b> submit= MYMASK=`printf '0x%x' \$((1<<\$SPECCOPYNUM))`; /usr/bin/taskset \$MYMASK $command </b></p>
<p>
       When running multiple copies of benchmarks, the SPEC config file feature 
       <b>submit</b> 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:
       <ul>
       <li> <b>/usr/bin/taskset [options] [mask] [pid | command [arg] ... ]</b>: <br />
           taskset is used to set or retreive the CPU affinity of a running 
           process given its PID or to launch a new COMMAND with a given CPU 
           affinity. The CPU affinity is represented as a bitmask, with the 
           lowest order bit corresponding to the first logical CPU and highest
           order bit corresponding to the last logical CPU. When the taskset 
           returns, it is guaranteed that the given program has been scheduled
           to a legal CPU. <br /><br />

           The default behaviour of taskset is to run a new command with a 
           given affinity mask: <br /><br />

                taskset [mask] [command] [arguments] </li>
       <li> <b>$MYMASK</b>: The bitmask (in hexadecimal) corresponding to a specific
           SPECCOPYNUM. For example, $MYMASK value for the first copy of a 
           rate run will be 0x00000001, for the second copy of the rate will 
           be 0x00000002 etc. Thus, the first copy of the rate run will have a
           CPU affinity of CPU0, the second copy will have the affinity CPU1 
           etc.</li>
       <li> <b>$command</b>: Program to be started, in this case, the benchmark instance 
               to be started. </li>
        </ul>
</p>

         <p><b>Using numactl to bind processes and memory to cores</b></p>
         <p>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.</p>
         <p>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'</p>

         <p><b>submit= $[top]/mysubmit.pl $SPECCOPYNUM "$command" </b></p>
         <p> 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.

         <ul><b>Source</b><br />

         ******************************************************************************************************<br />
<pre>

#!/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(&lt;INPUT&gt;)
{
  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";

</ul></pre></p>

<p><b>ulimit -s &lt;n | unlimited&gt;</b></p>
<p>
           Sets the stack size to <b>n</b> kbytes, or <b>unlimited</b> to allow the stack size 
           to grow without limit. </p>

<p><b> KMP_STACKSIZE=integer[B|K|M|G|T]</b></p>
<p>
           Sets the number of bytes to allocate for each parallel thread to use as its 
           private stack. Use the optional suffix B, K, M, G, or T, to specify bytes, 
           kilobytes, megabytes, gigabytes, or terabytes. The default setting is 2M on 
           IA32 and 4M on IA64. </p>

         <p><b>KMP_AFFINITY </b></p>
         <p>
         KMP_AFFINITY  =  &lt; physical | logical &gt;, starting-core-id <br/>
         specifies the static mapping of user threads to physical cores. For example,
         if you have a system configured with 8 cores, OMP_NUM_THREADS=8 and
         KMP_AFFINITY=physical,0 then thread 0 will mapped to core 0, thread 1 will be mapped to core 1, and
         so on in a round-robin fashion.   <br/> </p>

         <p>
         KMP_AFFINITY = granularity=fine,scatter <br/>
         The value for the environment variable KMP_AFFIINTY affects how the threads from an auto-parallelized program are scheduled across processors. <br/>
         Specifying granularity=fine selects the finest granularity level, causes each OpenMP thread to be bound to a single thread context. <br/>
         This ensures that there is only one thread per core on cores supporting HyperThreading Technology<br/>
         Specifying scatter distributes the threads as evenly as possible across the entire system. <br/>
         Hence a combination of these two options, will spread the threads evenly across sockets, with one thread per physical core. <br/>
         </p>

<p><b> OMP_NUM_THREADS=n  </b></p>
<p>
           This Environment Variable sets the maximum number of threads to use for OpenMP* 
           parallel regions to <b>n</b> if no other value is specified in the application. This 
           environment variable applies to both -openmp and -parallel (Linux) 
           or /Qopenmp and /Qparallel (Windows). Example syntax on a Linux system with 8 
           cores:<br>
           export OMP_NUM_THREADS=8<br>
           Default is the number of cores visible to the OS. 

    </p>


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</platform_settings>


</flagsdescription>