[Rocks-Discuss] Use of Memory

[xavier]

Hi all,

We have 5.3 rocks running on a 20 nodes cluster. Charging it full power
we noticed that no more memory was free one the frontend (we do not
compute on frontend).
Frontend memory is 16Gb, 1Gb is used and 15Gb are Memory Cached .

What does it mean?
Is that normal ?

thanks in advance.

Xavier

[Nick Holway]

Linux (and other modern OSs) caches files because it's quicker to
access them from RAM than disk. As you can imagine it's pointless to
have ~15GB of RAM unused. Linux will give the RAM that it is currently
caching with to another application when the application needs it.

Nick

[Mike Hanby]

For example, on our 16GB head node, the following is considered normal:

$ free -m
total used free shared buffers cached
Mem: 16047 15956 91 0 759 13480
-/+ buffers/cache: 1716 14330
Swap: 4094 0 4093

When looking at the output I interpret that to mean roughly 84% of the RAM is still available to applications.

[jean-francois prieur]

If you use the free command it will show you memory use without the
buffered memory

[root@golem jfprieur]# free -m

             total       used       free     shared    buffers     cached

Mem:          7971       5847       2123          0        154       4777
-/+ buffers/cache:        914       7056
Swap:          996          3        992

Regards,
JF

[xavier]

Thanks to all of us for answering, i was expecting that but it is always
good to be sure !
Regards
X.

jean-francois prieur a écrit :

[Nick Holway]

That's correct. The critical thing to look out for is that your server
isn't out of RAM and using the swap file. In your case it's using 0 MB
so you've got nothing to worry about.