About cache


In this article, you can find how to check cache size, free cache and check which files are cached.

Check cache size

According to specific requirements, we can check cache size by using:

$cat /proc/cpuinfo

$cat /proc/meminfo

$lscpu | grep cache

$dmesg | grep cache

$getconf -a | grep CACHE

cat /sys/devices/system/cpu/cpu0/cache/index1/size (level 1) cat /sys/devices/system/cpu/cpu0/cache/index2/size (level 2) cat /sys/devices/system/cpu/cpu0/cache/index3/size (level 3)

  • Some device may not have level 3 cache.
  • Or check ‘/sys/devices/system/cpu/cpu0/cache’, maybe you can find ‘index0’ as well. We can get to know which level it belongs by cat /sys/devices/system/cpu/cpu0/cache/index0/level .


$ lscpu | grep cache
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              20480K


$ lstopo-no-graphics

$ hwloc-ls

(may require install packages: hwloc, hwloc-nox)

Free cache

  • Free pagecache:

$ sudo sh -c 'echo 1 >/proc/sys/vm/drop_caches'

  • Free dentries and inodes:

$ sudo sh -c 'echo 2 >/proc/sys/vm/drop_caches'

  • Free free page cache, dentries and inodes:

$ sudo sh -c 'echo 3 >/proc/sys/vm/drop_caches'

What’s in cache

If you’d like to analyze the contents of the buffers & cache, to see what are currently being cached, you can try linux-ftools. If you cannot not open google, you can check out github repo of linux-ftools.

$ git clone https://github.com/xiaoyanzhuo/linux-ftools

After you get the linux-ftools, READ file ‘INSTALL’ and follow the instruction inside. Briefly, what you need to do:

$ cd linux-ftools
$ ./configure
$ make
$ make install

It works well when I installed it on regular linux server. However, on embeding system, I got fatal error when make the files, showing cannot find #include <asm/unistd_64.h>. Check $find /usr/src/linux-headers-* -name 'unistd*.h' and make sure build tools $sudo apt-get update, $sudo apt-get install build-essential. Tried other ways found online but none of them worked. The solution for my case: I just comment out the line #include <asm/unistd_64.h> in ‘fadvise.c’ and ‘fallocate.c’, the files mentioned in error information.

Finally, we have linux-ftools installed and can use it now.

Go to the dir in which you want to check what files are cached:

$ fincore --pages=false --summarize --only-cached *


$ cd ~/test_dir/
$ fincore --pages=false --summarize --only-cached *
filename size   total pages     cached pages    cached size     cached percentage
bikegray_6400x4800.pgm 30720056 7501 7501 30724096 100.000000
total cached size: 123404288
$ sudo sh -c 'echo 1 >/proc/sys/vm/drop_caches'
$ fincore --pages=false --summarize --only-cached *
filename size   total pages     cached pages    cached size     cached percentage
total cached size: 0
  1. empty-the-buffers-and-cache-on-a-linux-system
  2. linux-ftools on code.google