Bdtyktl

I wanted to know how to find L2 cache size in Linux...

for L1 cache size, I am doing the following

pico /proc/cpuinfo

what about L2 cache size?

cat /sys/devices/system/cpu/cpu0/cache/index2/size

or check dmidecode

or use lshw

EDIT 3: Heh, sorry, just do sudo dmidecode -t cache and it will show you your CPU's cache information. To tell what section you are looking at (L1 or L2), look at the Configuration: line. You want Configuration: Enabled, Not Socketed, Level 2.

You should check the following tool. It gives the most accurate information from all the tools I've tried.
This is the command line version output:

~$ lstopo-no-graphics

Machine (7984MB)

  Socket L#0

    L2 L#0 (4096KB)

      L1d L#0 (32KB) + L1i L#0 (32KB) + Core L#0 + PU L#0 (P#0)

      L1d L#1 (32KB) + L1i L#1 (32KB) + Core L#1 + PU L#1 (P#1)

    L2 L#1 (4096KB)

      L1d L#2 (32KB) + L1i L#2 (32KB) + Core L#2 + PU L#2 (P#2)

      L1d L#3 (32KB) + L1i L#3 (32KB) + Core L#3 + PU L#3 (P#3)

And this is the graphical interface:

Just use: lscpu

Sample output:

$ lscpu 

Architecture:          x86_64

CPU op-mode(s):        32-bit, 64-bit

Byte Order:            Little Endian

CPU(s):                4

On-line CPU(s) list:   0-3

Thread(s) per core:    1

Core(s) per socket:    4

Socket(s):             1

NUMA node(s):          1

Vendor ID:             GenuineIntel

CPU family:            6

Model:                 42

Stepping:              7

CPU MHz:               3401.000

BogoMIPS:              6784.57

Virtualization:        VT-x

L1d cache:             32K

L1i cache:             32K

L2 cache:              256K

L3 cache:              8192K

NUMA node0 CPU(s):     0-3

dmesg | grep cache will show your L1 and L2 related information.

getconf

getconf -a | grep CACHE

gives:

LEVEL1_ICACHE_SIZE                 32768

LEVEL1_ICACHE_ASSOC                8

LEVEL1_ICACHE_LINESIZE             64

LEVEL1_DCACHE_SIZE                 32768

LEVEL1_DCACHE_ASSOC                8

LEVEL1_DCACHE_LINESIZE             64

LEVEL2_CACHE_SIZE                  262144

LEVEL2_CACHE_ASSOC                 8

LEVEL2_CACHE_LINESIZE              64

LEVEL3_CACHE_SIZE                  20971520

LEVEL3_CACHE_ASSOC                 20

LEVEL3_CACHE_LINESIZE              64

LEVEL4_CACHE_SIZE                  0

LEVEL4_CACHE_ASSOC                 0

LEVEL4_CACHE_LINESIZE              0

Or for a single level:

getconf LEVEL2_CACHE_SIZE

The cool thing about this interface is that it is just a wrapper around the POSIX sysconf C function (cache arguments are non-POSIX extensions), and so it can be used from C code as well.

Tested in Ubuntu 16.04.

x86 CPUID instruction

The CPUID x86 instruction also offers cache information, and can be directly accessed by userland: https://en.wikipedia.org/wiki/CPUID

glibc seems to use that method for x86. I haven't confirmed by step debugging / instruction tracing, but the source for 2.28 sysdeps/x86/cacheinfo.c does that:

__cpuid (2, eax, ebx, ecx, edx);

TODO create a minimal C example, lazy now, asked at: https://stackoverflow.com/questions/14283171/how-to-receive-l1-l2-l3-cache-size-using-cpuid-instruction-in-x86