Topic
  • 2 replies
  • Latest Post - ‏2013-10-30T15:28:58Z by Bill_Buros
Bill_Buros
Bill_Buros
159 Posts

Pinned topic What's the cache line size on a 7R2 system?

‏2013-10-25T12:27:16Z |

Got a question last night..

What's the cache line size on a 7R2 system?

There are a number of cache levels on the processor cores, so here's some tips.   

On the system itself, you can check this.    This is an example from a 16-core POWER7+ 7R2 system.

# cd /proc/device-tree/cpus/
# ls -d *cache* 
l2-cache@2000  l2-cache@2007  l2-cache@200e  l3-cache@3105  l3-cache@310c
l2-cache@2001  l2-cache@2008  l2-cache@200f  l3-cache@3106  l3-cache@310d
l2-cache@2002  l2-cache@2009  l3-cache@3100  l3-cache@3107  l3-cache@310e
l2-cache@2003  l2-cache@200a  l3-cache@3101  l3-cache@3108  l3-cache@310f
l2-cache@2004  l2-cache@200b  l3-cache@3102  l3-cache@3109
l2-cache@2005  l2-cache@200c  l3-cache@3103  l3-cache@310a
l2-cache@2006  l2-cache@200d  l3-cache@3104  l3-cache@310b
# ls -d l2-cache* | wc -l
16
# ls -d l3-cache* | wc -l
16
 

Picking one of the l2-cache directories..  hex x'80' is 128 bytes.

# cd l2-cache\@2000
[l2-cache@2000]# ls
cache-unified      d-cache-size  i-cache-line-size  l2-cache       reg
d-cache-line-size  device_type   i-cache-sets       linux,phandle  status
d-cache-sets       ibm,phandle   i-cache-size       name
[l2-cache@2000]# cat d-cache-line-size | hexdump
0000000 0000 0080                              
0000004
[l2-cache@2000]# cat i-cache-line-size | hexdump
0000000 0000 0080                              
0000004
 

Checking the l3cache

# cd ../l3-cache\@3100/
[l3-cache@3100]# ls
cache-unified      d-cache-size  i-cache-line-size  linux,phandle  status
d-cache-line-size  device_type   i-cache-sets       name
d-cache-sets       ibm,phandle   i-cache-size       reg
[l3-cache@3100]# cat d-cache-line-size | hexdump
0000000 0000 0080                              
0000004
[root@3qjuno3 l3-cache@3100]# cat i-cache-line-size | hexdump
0000000 0000 0080                              
0000004
 

 

  • Bill_Buros
    Bill_Buros
    159 Posts
    ACCEPTED ANSWER

    Re: What's the cache line size on a 7R2 system?

    ‏2013-10-25T12:31:32Z  

    For more details on the system and processor designs, we also recommend the Redbook:  IBM Power 710 and 730 Technical Overview and Introduction

    http://www.redbooks.ibm.com/abstracts/redp4983.html?Open

    There's a good description of memory bandwidth and cache in the memory sections.   Check out Chapter 2.3.3 Memory Bandwidth.

  • Bill_Buros
    Bill_Buros
    159 Posts

    Re: What's the cache line size on a 7R2 system?

    ‏2013-10-25T12:31:32Z  

    For more details on the system and processor designs, we also recommend the Redbook:  IBM Power 710 and 730 Technical Overview and Introduction

    http://www.redbooks.ibm.com/abstracts/redp4983.html?Open

    There's a good description of memory bandwidth and cache in the memory sections.   Check out Chapter 2.3.3 Memory Bandwidth.

  • Bill_Buros
    Bill_Buros
    159 Posts

    Re: What's the cache line size on a 7R2 system?

    ‏2013-10-30T15:28:58Z  

    Got a clarification from the engineering team as well..

     

    All IBM Power systems are 128 byte cachelines.