Re: Memory usage Debian Jessie (stable)

You can drop the cache with this command:

sync; echo 3 > /proc/sys/vm/drop_caches

See what it does at my laptop:

root@laptop:~# free -m

total used free shared buffers cached

Mem: 7439 3029 4409 201 91 1368

-/+ buffers/cache: 1569 5870

Swap: 1906 0 1906

root@laptop:~# sync; echo 3 > /proc/sys/vm/drop_caches

root@laptop:~# free -m

total used free shared buffers cached

Mem: 7439 2001 5437 194 2 480

-/+ buffers/cache: 1518 5920

Swap: 1906 0 1906

As you can see, the cache was reduced from 1368 to 480, "freeing" more than 1GB, but on the second line the free ammount remains the same because, as Dan said, it ignores the cache.

2015-05-11 11:50 GMT-03:00 Dan Christensen <jdc@uwo.ca>:

Jan-Rens Reitsma <jan.rens.reitsma@gmail.com> writes:

> $ free -h
> total used free shared buffers cached
> Mem: 3.7G 3.5G 182M 153M 363M 2.1G
> -/+ buffers/cache: 1.0G 2.7G
> Swap: 7.6G 0B 7.6G
>
> 3.5 GB used of 3.7 GB available memory,
> with 2.1 GB available for caching and 182 MB free,
> 1.0 GB of the available cache and memory is used,
> no swap space used.

That's not a correct interpretation of the output of "free". What that
output says is that 3.5GB is used, but of that, 363MB + 2.1GB = 2.5GB is
currently being used for buffers and cache. The memory used for buffers
and cache can be made available very quickly, so the second line shows
how much is used (1.0GB) and free (2.7GB) with the buffer and cache
usage ignored. So the real thing to take away from the above is in
the second line: only 1.0GB is used and 2.7GB is free. See

http://unix.stackexchange.com/questions/33541/free-output-format/33549#33549

Dan

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