Question

Hi

I am looking for a command to check for on-chip L3 cache size on a unix system.

Thanks Bi

Answer 1

look at '/proc/cpuinfo'

Answer 2

Take a look at dmidecode, which has an excellent man page.

Look for an entry named "Processor Information", mine reads:

Handle 0x0004, DMI type 4, 35 bytes
Processor Information
    ...
    L1 Cache Handle: 0x0008
    L2 Cache Handle: 0x0009
    L3 Cache Handle: Not Provided
    ...

This tells me to look for the handle 0x0009 (for L2 cache, since I don't have any L3). This reads:

Handle 0x0009, DMI type 7, 19 bytes
Cache Information
    Socket Designation: L2 Cache
    Configuration: Enabled, Socketed, Level 2
    Operational Mode: Write Back
    Location: External
    Installed Size: 2048 KB
    Maximum Size: 2048 KB
    Supported SRAM Types:
    	Burst
    	Pipeline Burst
    	Asynchronous
    Installed SRAM Type: Burst
    Speed: Unknown
    Error Correction Type: Unknown
    System Type: Unknown
    Associativity: Unknown

Answer 3

If all else fails, just use /proc/cpuinfo or any other method to find the model number of your processor, and look that up on google to find the specs.

Answer 4

On recent Linux kernels running on the x86 architecture, you can probably find the information you want at /sys/devices/system/cpu/cpu#/cache (replace the # by the CPU number). For instance, on this computer (which does not have a L3 cache):

$ cat /sys/devices/system/cpu/cpu0/cache/index0/level 
1
$ cat /sys/devices/system/cpu/cpu0/cache/index0/type 
Data
$ cat /sys/devices/system/cpu/cpu0/cache/index0/size 
64K
$ cat /sys/devices/system/cpu/cpu0/cache/index1/level
1
$ cat /sys/devices/system/cpu/cpu0/cache/index1/type 
Instruction
$ cat /sys/devices/system/cpu/cpu0/cache/index1/size 
64K
$ cat /sys/devices/system/cpu/cpu0/cache/index2/level 
2
$ cat /sys/devices/system/cpu/cpu0/cache/index2/type 
Unified
$ cat /sys/devices/system/cpu/cpu0/cache/index2/size 
512K

This corresponds to a L1 data cache of 64K, a L1 instruction cache of 64K, and a L2 instruction+data cache of 512K. Note that this is more detailed than /proc/cpuinfo, which only says cache size : 512 KB. There are several other files in these cache/index# directories with even more detail.

Please read Documentation/ABI/README and Documentation/ABI/testing/sysfs-devices-system-cpu before using these files; in particular, they do not seem to be a stable ABI, and thus might become missing in the future. They come from arch/x86/kernel/cpu/intel_cacheinfo.c, which uses cpuid to directly get the information (meaning that, when present, they should be more reliable than dmidecode).