How to clear cache memory in RHEL4?

tcegrid · 10-20-2008, 12:35 PM

Hi All,
I am using RHEL4. When I give the free command. It gives following output.

total used free shared buffers cached
Mem: 32710352 6168032 26542320 0 144216 5464628
-/+ buffers/cache: 559188 32151164
Swap: 2040212 0 2040212

Here it seems cache memory occupies 5GB of memory.
Can anyone tell me how to clear this cache memory?

Regards,
Thamizh

CRC123 · 10-20-2008, 01:11 PM

Pretty much the same question asked here.

Don't worry about it.

JSkywalker · 10-20-2008, 02:04 PM

my 'free' shows:
$ free
total used free shared buffers cached
Mem: 3974852 3909092 65760 0 115240 2278888
-/+ buffers/cache: 1514964 2459888
Swap: 4070544 128 4070416

What is the main purpose of your machine?
mine runs Apache/MySQL/Postfix

i wonder, why you cache is so much higher than mine...

CRC123 · 10-20-2008, 02:10 PM

Quote:

Originally Posted by JSkywalker

my 'free' shows:
$ free
total used free shared buffers cached
Mem: 3974852 3909092 65760 0 115240 2278888
-/+ buffers/cache: 1514964 2459888
Swap: 4070544 128 4070416

What is the main purpose of your machine?
mine runs Apache/MySQL/Postfix

i wonder, why you cache is so much higher than mine...

Well first of all, he has close to 32GB of memory while you only have around 4GB but yet you are still 'using' more memory than he is.

I bet that the buffering/caching algorithm will allocate more buffer/cache memory the more RAM you have (it make's since at least).

icorson · 10-20-2008, 02:22 PM

sudo sync
sudo echo 3 | sudo tee /proc/sys/vm/drop_caches

JSkywalker · 10-20-2008, 03:06 PM

Quote:

Originally Posted by CRC123

Well first of all, he has close to 32GB of memory

damn, i must have overlooked one digit...

chrism01 · 10-20-2008, 07:38 PM

Frankly, I'd leave it alone. The kernel/scheduler knows what its doing. It will use all the memory it can find and shuffle things in/out on demand. There's no point in trying to do it manually.