Re: Process memory behaviour of Oracle
From: Robert Klemme <shortcutter_at_googlemail.com>
Date: Mon, 14 Jan 2008 23:00:59 +0100
Message-ID: <5v24ctF1jb81jU1@mid.individual.net>
>
> Thanks Jonathan!
>
> In the meantime I have also noted the following: when I check v
> $pgastats I notice a huge entry for memory freed/released to OS
> (suspiciously close to the 10G I released earlier) - I am guessing
> that Oracle "holds on" to PGA memory for a while and does not let the
> OS have it back ?
>
> From what I understand of the Linux memory allocator it masks system
> brk() calls inside the library malloc() for efficiency reaons so
> perhaps Oracle does something similar ? But one problem I have is that
> the SGA sometimes has problems acquiring memory (I see this in the
> stack trace of a Java OJDBC driver when it tries to set up connections
> etc.) even though my own C program does not (i.e., I believe the
> memory is there to be had)
>
> ...but first I must study your link!
Date: Mon, 14 Jan 2008 23:00:59 +0100
Message-ID: <5v24ctF1jb81jU1@mid.individual.net>
On 14.01.2008 19:41, pidmky_at_gmail.com wrote:
> On Jan 14, 6:21 pm, "Jonathan Lewis" <jonat..._at_jlcomp.demon.co.uk>
> wrote:
>> The presentation and notes at the following URL may help:http://www.pythian.com/blogs/741/pythian-goodies-free-memory-swap-ora... >> >> -- >> Regards >> >> Jonathan Lewishttp://jonathanlewis.wordpress.com
>
> Thanks Jonathan!
>
> In the meantime I have also noted the following: when I check v
> $pgastats I notice a huge entry for memory freed/released to OS
> (suspiciously close to the 10G I released earlier) - I am guessing
> that Oracle "holds on" to PGA memory for a while and does not let the
> OS have it back ?
>
> From what I understand of the Linux memory allocator it masks system
> brk() calls inside the library malloc() for efficiency reaons so
> perhaps Oracle does something similar ? But one problem I have is that
> the SGA sometimes has problems acquiring memory (I see this in the
> stack trace of a Java OJDBC driver when it tries to set up connections
> etc.) even though my own C program does not (i.e., I believe the
> memory is there to be had)
>
> ...but first I must study your link!
Some additional food for thought:
http://christianbilien.wordpress.com/2008/01/06/where-has-all-my-memory-gone/
Kind regards
robert Received on Mon Jan 14 2008 - 16:00:59 CST