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<!DOCTYPE flagsdescription SYSTEM "http://www.spec.org/dtd/cpuflags1.dtd">
<flagsdescription>

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<filename>Cryo-platform-linux64-revA.xml</filename>

<title>SPEC CPU2006 Flag Description for Cryo Platform Servers and Workstations</title>

<platform_settings>
 <![CDATA[ 
	 <p><b>Platform settings</b></p>

         <p>One or more of the following settings may have been set.  If so, the "General 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>Linux Huge Page settings</b></p>
	 <p>In order to take advantage of large pages, your system must be configured to use large pages.
		To configure your system for huge pages perform the following steps:</p>
		 <ul>
		   <li>Create a mount point for the huge pages: "mkdir /mnt/hugepages"</li>
		   <li>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"</li>
		   <li>Set vm/nr_hugepages=N in your /etc/sysctl.conf file where N is the maximum number of pages the system may allocate.</li>
		   <li>Reboot to have the changes take effect.(Not necessary on some operating systems like RedHat Enterprise Linux 5.5.</li>
		 </ul>

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

	 <p><b>HUGETLB_MORECORE </b></p>
	 <p>
	 Set this environment variable to "yes" to enable applications to use large pages. 
	 </p>

         <p><b>LD_PRELOAD=/usr/lib64/libhugetlbfs.so </b></p>
         <p>
         Setting this environment variable is necessary to enable applications to use large pages. 
	 </p>


         <p><b>KMP_STACKSIZE </b></p>
         <p>
         Specify stack size to be allocated for each thread. 
	 </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_AFFINITY 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 </b></p>
         <p>
	  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
          </p>

	<p><b>Intel&#0174; HyperThreading Technology</b></p>
	<p>Intel&#0174; Hyper-Threading Technology (Intel&#0174; HT Technology) potentially uses processor resources more efficiently, enabling multiple threads to 
	run on each core. Intel&#0174; HT Technology potentially increases processor throughput, improving overall performance on threaded software.  Intel&#0174; HT
	Technology can be user enabled and disabled in the BIOS as required.</p>

         <p><b>ulimit -s &lt;n&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>submit= MYMASK=`printf '0x%x' $((1&lt;&lt;$SPECCOPYNUM))`; /usr/bin/taskset $MYMASK $command </b></p>
	 <p>When running multiple copies of benchmarks, the SPEC config file feature 
	 <b>submit</b> is sometimes used to cause individual jobs to be bound to 
	 specific processors. This specific submit command is used for Linux. 
	 The description of the elements of the command are:</p>
	 <ul>
	 <li><b>/usr/bin/taskset [options] [mask] [pid | command [arg] ... ]</b>: <br/>
       	 taskset is used to set or retreive the CPU affinity of a running 
         process given its PID or to launch a new COMMAND with a given CPU 
         affinity. The CPU affinity is represented as a bitmask, with the 
         lowest order bit corresponding to the first logical CPU and highest
         order bit corresponding to the last logical CPU. When the taskset 
         returns, it is guaranteed that the given program has been scheduled
         to a legal CPU.<br/>
         The default behaviour of taskset is to run a new command with a 
         given affinity mask: <br/>
         taskset [mask] [command] [arguments]</li>
	 <li><b>$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><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>

  ]]> 
</platform_settings>

</flagsdescription>