current community

your communities

more stack exchange communities

Stack Exchange
tour help
Take the 2-minute tour ×
Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems.. It's 100% free, no registration required.
up vote 0 down vote favorite

I am aware that sync command flushes the dirty cache into disk. I have run free command first, then sync, and then free again. The result of latter free command shows more free memory available than the former one.

Does this mean that the dirty caches are removed from memory when performing sync? Can anybody give me a more solid proof?

share|improve this question
    
Related: How do you empty the buffers and cache on a Linux system? –  slm Aug 27 '13 at 6:54
add comment

1 Answer

up vote 0 down vote

This will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free.

To free pagecache:

echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:

echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:

echo 3 > /proc/sys/vm/drop_caches

As this is a non-destructive operation, and dirty objects are not freeable, the user should run "sync" first in order to make sure all cached objects are freed.

share|improve this answer
    
Source: kernel.org/doc/Documentation/sysctl/vm.txt –  Evan Teitelman Aug 27 '13 at 5:59
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.