topic Re: Question on swap in Operating System - Linux

Question on swap

praveen.. — Wed, 18 Oct 2006 23:53:07 GMT

Hi Friends,
On Linux it appears that two instances of AS are taking 10 GB of RAM, at least TOP shows this and I’m worried about swapping occurring as I think I have seen the swap process kick in. Bu the Swap total has never gone over 224K. Now these two models on Windows are taking only about 1.2 GB, so why do you think Linix would be showing 10 GB of memory used?

top - 23:53:03 up 36 days, 18:03, 1 user, load average: 0.24, 0.05, 0.02
Tasks: 174 total, 1 running, 173 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.3% us, 0.3% sy, 0.0% ni, 98.3% id, 1.1% wa, 0.0% hi, 0.0% si
Mem: 10233436k total, 10165620k used, 67816k free, 114136k buffers
Swap: 50331636k total, 224k used, 50331412k free, 2106540k cached

Re: Question on swap

Stuart Browne — Thu, 19 Oct 2006 00:50:11 GMT

So, the machine has 10GB of RAm, of which most of it is being used.

By AS, I'm going to assume you're talking about Oracle Application Server. From what I've seen of Oracle, it'll use what memory is available to do buffers and caching internally. Without seeing the process listing, it's hard to tell if that's what it's doing (it also depends on the tuning).

Linux it's self will also do this to some extent. Things to note:

2106540k cached - 2GB in disk cache.
114136k buffers - A further 100MB in disk buffers.

Using 'top', you can sort-by-memory (M) to give an idea of the top users.

So, more details will help us give more accurate answers..

Re: Question on swap

Vitaly Karasik_1 — Thu, 19 Oct 2006 02:39:18 GMT

your situation (all RAM is used, swap is free) is OK. Why all RAM is used? - linux kernel takes all available RAM for bufferes and cache.

Re: Question on swap

praveen.. — Thu, 19 Oct 2006 05:53:40 GMT

this is the process list:

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4361 root 15 0 32144 18m 1588 S 0.3 0.2 14:40.20 hald
13414 root 16 0 36128 2776 2108 S 0.3 0.0 0:00.05 sshd
1 root 16 0 4748 560 464 S 0.0 0.0 0:01.21 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.96 migration/0
3 root 34 19 0 0 0 S 0.0 0.0 0:01.13 ksoftirqd/0
4 root RT 0 0 0 0 S 0.0 0.0 0:00.34 migration/1
5 root 34 19 0 0 0 S 0.0 0.0 0:01.55 ksoftirqd/1
6 root RT 0 0 0 0 S 0.0 0.0 0:00.10 migration/2
7 root 34 19 0 0 0 S 0.0 0.0 0:00.22 ksoftirqd/2
8 root RT 0 0 0 0 S 0.0 0.0 0:00.15 migration/3
9 root 34 19 0 0 0 S 0.0 0.0 0:01.32 ksoftirqd/3
10 root RT 0 0 0 0 S 0.0 0.0 0:00.17 migration/4
11 root 34 19 0 0 0 S 0.0 0.0 0:01.26 ksoftirqd/4
12 root RT 0 0 0 0 S 0.0 0.0 0:00.15 migration/5
13 root 34 19 0 0 0 S 0.0 0.0 0:00.52 ksoftirqd/5
14 root RT 0 0 0 0 S 0.0 0.0 0:00.07 migration/6
15 root 34 19 0 0 0 S 0.0 0.0 0:00.18 ksoftirqd/6
16 root RT 0 0 0 0 S 0.0 0.0 0:00.10 migration/7
17 root 34 19 0 0 0 S 0.0 0.0 0:00.32 ksoftirqd/7
18 root 5 -10 0 0 0 S 0.0 0.0 0:00.01 events/0
19 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/1
20 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/2
21 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/3
22 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/4
23 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/5
24 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/6
25 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 events/7
26 root 5 -10 0 0 0 S 0.0 0.0 0:00.01 khelper
27 root 14 -10 0 0 0 S 0.0 0.0 0:00.00 kacpid
57 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/0
58 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/1
59 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/2
60 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/3
61 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/4
62 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/5
63 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/6
64 root 5 -10 0 0 0 S 0.0 0.0 0:00.00 kblockd/7

Re: Question on swap

Vitaly Karasik_1 — Thu, 19 Oct 2006 06:56:05 GMT

you don't have memory-intensive processes in your top output.
do you really run Oracle?

Re: Question on swap

Ivan Ferreira — Thu, 19 Oct 2006 08:02:17 GMT

You don't have to worry about memory usage unless you have page in AND page out in the ouput of the vmstat command. If you do have it, then the system is paging/swapping and this reduces the performance.

If your system is performing whell, and is not swapping, then you don't have a memory issue.