Re: Physical Memory Fully Used and Swap is Not Used
Date: Tue, 23 Jun 2009 09:15:43 -0400
Message-ID: <3678d6530906230615ga43464ep4d0399a4c40e115a_at_mail.gmail.com>
ps on linux tells you the aggregate size of the process. Try adding up all of what you see and you'll quickly realize that it is a pack of lies when the sum is much much greater than physical memory. The trick is that linux is pretty good about sharing pages (copy on write/etc) between processes.
As for main memory, you can start with "free" and look at what is available w/o caches.
A few things: the original poster hasn't really given enough information which would help out quite a bit.
- which version of redhat
- 32bit or 64bit? if not 64bit, why not?
- are hugepages being used for the sga? if not, why not? if so, how many are allocated? how many are in use? (cat /proc/meminfo to look)
- what are the relevent sga/cache size settings for this instance?
- has the op scoured metalink regarding that pmon error and/or openned an
SR?
- craig
On Tue, Jun 23, 2009 at 3:29 AM, Yechiel Adar <adar666_at_inter.net.il> wrote:
> I think that ps that shows the memory usage of all processes in the server
> is in order.
>
> Adar Yechiel
> Rechovot, Israel
>
>
>
> Mudhalvan Moovarkku wrote:
>
> Mathias,
>
>
>
> Thanks for your mail.
>
>
>
> Yes I do understand. Now I have two clarifications.
>
>
>
> 1. Problem is at this point instead of using Swap My server response
> time was very slow and PMON process failed with the message at alert “PMON
> failed to acquire latch” and DB went down.
>
>
>
> 2. In 8.0.6 on Unix used only 7GB Memory but why in 10.2.0.4 on
> Linux uses more than 16GB
>
>
>
> Regards
>
> Mudhalvan M.M
>
>
> ------------------------------
>
> *From:* mathiasmag_at_gmail.com [mailto:mathiasmag_at_gmail.com<mathiasmag_at_gmail.com>]
> *On Behalf Of *Mathias Magnusson
> *Sent:* Tuesday, June 23, 2009 3:15 PM
> *To:* Mudhalvan Moovarkku
> *Cc:* oracle-l_at_freelists.org
> *Subject:* Re: Physical Memory Fully Used and Swap is Not Used
>
>
>
> Are you trying to tune or to understand memory? There is nothing here that
> would indicate a problem. If you use all you memory and no swap, then that
> would be optimal. It shows that your box is sized perfectly and you do not
> ned to use swap. Using swap reduces performance (if we compare to having
> enough memory and not needing swap).
>
>
>
> If on the other hand you motivation is to understand why these numbers
> would be this way, then someone who has spent more time reading RDAs on
> Linux would need to answer here. To me the numbers would indicate that you
> have just barely reached the point where swap is starting to be used when
> more memory is needed.
>
>
> Mathias
> http://mathiasmagnusson.com
> http://blog.mathiasmagnusson.com
> http://photo.mathiasmagnusson.com
> http://oradbdev.mathiasmagnusson.com
>
> On Tue, Jun 23, 2009 at 7:41 AM, Mudhalvan Moovarkku <
> moovarkku.mudhalvan_at_axa-direct.co.jp> wrote:
>
> Dear DBAs,
>
> We have recently migrated Oracle from 8.0.6 on HP-Unix to 10.2.0.4
> on Red Hat Linux
>
> Earlier the same application worked fine with 7GB RAM on HP-UNIX
> on PA-RISC
>
> Upgraded system on IBM X 3850 with 16GB RAM but still we have some
> performance issue.
>
> I knew there is some lagging because of Hardware Architecture but
> it is too bad 7 GB to 16GB RAM but still have performance.
>
> Please look at data collected from RDA. Looking at this scenario
> my physical memory is fullly used but Swap is not at all used.
>
> Total Physical Memory 16032 MiB
>
> Available Physical Memory 30 MiB
>
> Swap: Max Size 24575 MiB
>
> Swap: Available 24505 MiB
>
> Swap: In Use 70 MiB
>
> We know there is some performance issue in application. I would
> like to make as much as possible from Database/Linux side tunning to provide
> atlease peaceful performance. Can any body through some light on why the
> swap is not at all used.
>
> Regards
>
> Mudhalvan M.M
>
>
>
>
--
.- ... . -.-. .-. . - -- . ... ... .- --. .
Craig I. Hagan
hagan(at)cih.com
"Those who can make you believe absurdities can make you commit atrocities."
Voltaire
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Received on Tue Jun 23 2009 - 08:15:43 CDT