Hi Kenan,
It sounds like you found the answer.
I just tried to run free -m on my small Linux box and found output
quite misleading ;(
May be somebody in the list would help to interpret it.
From first line i understood that i have 591 MB in total 584MB used
and almos no free memory.
From "-/+ buffers/cache" 368 from 584 is used for FS cache, leaving
222 for anything else.
Sounds like 222-6 - is used by applications on my host and not realy
free as reported in secound line.
output is mor interesting if we know that EBS environment is running
on that server :)
jurijs:~ # free -m
total used free shared buffers cached
Mem: 591 584 6 0 22 192
-/+ buffers/cache: 368 222
Swap: 776 665 110
jurijs:~ #
Thank you in advance,
Jurijs
On 5/20/07, Kenan Öztürk <mynameiskenan@xxxxxxxxx> wrote:
> Vasu,
>
> thanks for the helpful info.
> according to your reply, i googled for "cached" part of the top command.
> Here is a good explaination for memory usage:
>
> Overview of memory management
> Traditional Unix tools like 'top' often report a surprisingly small amount
> of free memory after a system has been running for a while. For instance,
> after about 3 hours of uptime, the machine I'm writing this on reports under
> 60 MB of free memory, even though I have 512 MB of RAM on the system. Where
> does it all go?
> The biggest place it's being used is in the disk cache, which is currently
> over 290 MB. This is reported by top as "cached". Cached memory is
> essentially free, in that it can be replaced quickly if a running (or newly
> starting) program needs the memory.
> The reason Linux uses so much memory for disk cache is because the RAM is
> wasted if it isn't used. Keeping the cache means that if something needs the
> same data again, there's a good chance it will still be in the cache in
> memory. Fetching the information from there is around 1,000 times quicker
> than getting it from the hard disk. If it's not found in the cache, the hard
> disk needs to be read anyway, but in that case nothing has been lost in
> time.
> To see a better estimation of how much memory is really free for
> applications to use, run the command free -m:
> The -/+ buffers/cache line shows how much memory is used and free from the
> perspective of the applications. Generally speaking, if little swap is being
> used, memory usage isn't impacting performance at all.
>
>
> Regards,
> Kenan
>
> Vasu Balla <appsdba@xxxxxxxxx> wrote:
> in linux, file system also maintains its cache, which gives us a feeling
> that whole memory getting filled up. infact when some other program requests
> for memory, the memory occupied by filesystem is automatically freed up and
> given to that process.
>
> top - 12:39:21 up 3 days, 20:23, 23 users, load average: 0.78, 1.04, 1.00
> Tasks: 266 total, 5 running, 261 sleeping, 0 stopped, 0 zombie
> Cpu(s): 75.5%us, 5.6%sy, 0.0%ni, 16.6%id, 2.3%wa, 0.0%hi, 0.0%si,
> 0.0%st
> Mem: 1035676k total, 995916k used, 39760k free, 85536k buffers
> Swap: 2096472k total, 144k used, 2096328k free, 416648k cached
> there are some kernel parameters which control the amt of memory that always
> needs to be kept free. can't get that param name from top of my head. you
> can google for it
>
> vasu
>
> -----Original Message-----
> From: ora-apps-dba-bounce@xxxxxxxxxxxxx
> [mailto:ora-apps-dba-bounce@xxxxxxxxxxxxx] On Behalf Of
> Kenan Öztürk
> Sent: Friday, May 18, 2007 7:39 PM
> To: ora-apps-dba@xxxxxxxxxxxxx
> Subject: memory usage
>
> Hi all,
>
> on RedHat A.S 3.0/4.0 I observer that free memory amount is really low. I
> know that if it is swapping then there's a problem otherwise it is normal.
> bu where this ram going?
>
> After rebooting system and starting ebs services, i observe that ram usage
> is increasing and only 10-50 mb free memory remains!
>
> Regards,
> Kenan
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