memory

Franck Pachot's picture

Kernel panic – not syncing: Out of memory and no killable processes

This is a quick post to give a solution (maybe not the best one as this was just quick troubleshooting) if, at boot, you see something like:
Trying to allocate 1041 pages for VMLINUZ [Linux=EFI, setup=0x111f, size=0x41108d01]
and then:
Kernel panic - not syncing: Out of memory and no killable processes
Pid: 1228 comm: kworker Not tainted 3.8.13-118.17.4.el6uek.x86_64 #2


IMG_E5543
If you do not see the messages, then you may need to remove the ‘quiet’ option of kernel and replace it by ‘nosplash’ – this is done from grub.

fritshoogland's picture

Introduction to pinatrace annotate version 2: a look into latches again

This post is an introduction to pinatrace annotate version 2, which is a tool to annotate the output of the Intel Pin tools ‘pinatrace’ tool.

The pinatrace tool generates a file with every single memory access of a process. Please realise what this means: this is every single read from main memory or write to main memory from the CPU. This allows you to get an understanding what happens within a C function. This means you can determine what information or data is accessed in what function. Needless to say this is a tool for internals investigations and research, not something for normal daily database maintenance and support. Also, the performance of the process that you attached to is severely impacted, and it can only be turned off by stopping the process. Do not use this on a production database, use this at your own risk for research and investigational purposes only.

fritshoogland's picture

Installation overview of node_exporter, prometheus and grafana

Prometheus is an open source systems monitoring and alerting toolkit originally build at Soundcloud. This blogpost shows how to install the needed components to do visualisation of linux system statistics via Grafana.

The setup consists of 3 components:
node_exporter, an exporter of system and hardware metrics.
prometheus, a metric collection and persistence layer.
grafana, the visualisation layer.

1. Preparation
The needed components are installed in the home directory of the user ‘prometheus’. In order for that user exist, it must obviously first be created:

fritshoogland's picture

Advanced Oracle memory profiling using pin tool ‘pinatrace’

In my previous post, I introduced Intel Pin. If you are new to pin, please follow this link to my previous post on how to set it up and how to run it.

One of the things you can do with Pin, is profile memory access. Profiling memory access using the pin tool ‘pinatrace’ is done in the following way:

$ cd ~/pin/pin-3.0-76991-gcc-linux
$ ./pin -pid 12284 -t source/tools/SimpleExamples/obj-intel64/pinatrace.so

The pid is a pid of an oracle database foreground process. Now execute something in the session you attached pin to and you find the ‘pinatrace’ output in $ORACLE_HOME/dbs:

fritshoogland's picture

How much memory is truly used by my Oracle instance?

There are many posts about the amount of memory that is taken by the Oracle database executables and the database SGA and PGA. The reason for adding yet another one on this topic is a question I recently gotten, and the complexities which surrounds memory usage on modern systems. The intention for this blogpost is to show a tiny bit about page sharing of linux for private pages, then move on to shared pages, and discuss how page allocation looks like with Oracle ASMM (sga_target or manual memory).

The version of linux in this blogpost is Oracle Linux 7.2, using kernel: 4.1.12-37.6.3.el7uek.x86_64 (UEK4)
The version of the Oracle database software is 12.1.0.2.160719 (july 2016).

fritshoogland's picture

Oracle system V shared memory indicated deleted

This article is written with examples taken from an (virtualised) Oracle Linux 6u6 X86_64 operating system, and Oracle database version 12.1.0.2.1. However, I think the same behaviour is true for Oracle 11 and 10 and earlier versions.

Probably most readers of this blog are aware that a “map” of mapped memory for a process exists for every process in /proc, in a pseudo file called “maps”. If I want to look at my current process’ mappings, I can simply issue:

fritshoogland's picture

Reading Oracle memory dumps

Every DBA working with the Oracle database must have seen memory dumps in tracefiles. It is present in ORA-600 (internal error) ORA-7445 (operating system error), system state dumps, process state dumps and a lot of other dumps.

This is how it looks likes:

fritshoogland's picture

Oracle database operating system memory allocation management for PGA – part 4: Oracle 11.2.0.4 and AMM

This is the 4th post in a series of posts on PGA behaviour of Oracle. Earlier posts are: here (PGA limiting for Oracle 12), here (PGA limiting for Oracle 11.2) and the quiz on using PGA with AMM, into which this blogpost dives deeper.

As laid out in the quiz blogpost, I have a database with the following specifics:
-Oracle Linux x86_64 6u6.
-Oracle database 11.2.0.4 PSU 4
-Oracle database (single instance) with the following parameter set: memory_target=1G. No other memory related parameters set.

fritshoogland's picture

Oracle database operating system memory allocation management for PGA – part 3: Oracle 11.2.0.4 and AMM: Quiz

This is a series of blogposts on how the Oracle database makes use of PGA. Earlier posts can be found here (PGA limiting for Oracle 12) and here (PGA limiting for Oracle 11.2).

Today a little wednesday fun: a quiz.

What do you think will happen in the following situation (leave a response as comment please!):

-Oracle Linux x86_64 6u6.
-Oracle database 11.2.0.4 PSU 4
-Oracle database (single instance) with the following parameter set: memory_target=1G. No other memory related parameters set.

jeremy.schneider's picture

November/December Highlights

In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over beers – justifying hotel and flight expenses by preparing technical presentations of their most interesting and recent problems or projects. UKOUG and DOAG happen shortly after OpenWorld with a similar (but more European) impact – and December seems to mingle the domino effect of tweets and blog posts inspired by the conference social activity with holiday anticipation at work.

I avoided any conference trips this year but I still noticed the usual surge in interesting twitter and blog activity. It seems worthwhile to record a few highlights of the past two months as the year wraps up.

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