This is post number 3 in a series of unanswered "TUNING" questions.
With AIX 5.3 TL4, the page size can vary from the original "4k". They can now be "64k" and a couple other sizes. They also do not have to all be the same. Some can remain "4k" while others are "64k" which is what seems to be going on in my system. Does anyone know of any advantages to moving from 4k sized pages to 64k sized pages? With my server having about 13 gig of memory, I think this can only help, right? It's an oracle database server.
You can see the size of your pages in memory with this command:
Here is what the output from my machine looks like. The page sizes are the last 2 lines:
The problem is that tuning questions are platform specific and we are a little short on AIX experts. But in general, large page sizes can waste a large percentage of a large page for every memory segment and that is the only downside. With 13 GB of physical memory you probably want a large page size and this is especially true with Oracle running. A large page size means that the cpu spends less time figuring out how to convert virtual addresses to physical addresses.
Large pages will help applications like Oracle in saving a lot of cpu time by reading / writing large pages instead of the smaller 4K pages , I think the pricess is called lrud which will save lots of cpu. I remember when we did it in the past, We designed the Oracle SGA to use all large pages and pinned. Please note that large pages does not support paging.
Yes, we did leave the rest of the memory [ Total - SGA ] in 4Ks. As IBM documented it can have serious impact to other applications if the page size is more than 4K.
So we will need sufficient memory. And make sure that all the large pages are allocated for the application which is capable of using it. Dont leave any large pages free. They must be pinned in the memory [ no paging ].
If you are talking about oracle, then I will implement large pages on a server which is dedicated for Oracle DB. Nothing else. If that is a webserver cum apps server and something else , I will not do that. The reason being complexity is designing and then maintaining.
Greetings,
i'm wondering if there is a way to determine minimum memory requirement for AIX kernel and OS functions? We use memdetails script from perfpmr package to see actual memory allocation, for example like this:
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I am not sure where to post this so i will put it in the newbie section.
I have set up a bog standard debain 6, LAMP environment in the cloud.
The specs
1 core at 2GH
2.5gb Memory
running Jommla, with about 1.6K visitors a day.
I am using AppFirst (appfirst.com) to monitor the... (2 Replies)
Hi everyone,
i have a question about the Memory Management in AIX 6.1.
I have
- 128 GB RAM and
- 70 GB Page Space.
The application i am running on this machine is doing some operations in perl. These are done only once a day and uses both memory and paging space. My problem... (1 Reply)
Hello,
I've been reading your forums for quite a while and the great amount of information I find here always come in hand.This time however, I need some specific help...
I have a doubt with an AIX server which I'm failing to understand as I'm new to its concept of memory management...
... (8 Replies)
I have to check whether AIX fills physical memory pages by zeros when they are given for a new process (or may be when they are freed from an address space, but it's hardly probable).
In other words when a process gets a new memory page, this one must be cleaned.
I've solved this issue for... (2 Replies)
We just set up a system to use large pages. I want to know if there is a command to see how much of the memory is being used for large pages. For example if we have a system with 8GB of RAm assigned and it has been set to use 4GB for large pages is there a command to show that 4GB of the *GB is... (1 Reply)
We have been tuning MySQL lately and I ran accoss two useful tools that you might be interested in:
mysqltuner.pl
tuning-primer.sh
Both of these scripts are quite useful for MySQL tuning. Here is some sample output of mysqltuner.pl
>> MySQLTuner 0.9.8 - Major Hayden... (3 Replies)
Hello,
I'm using a unix server (HP rp2450) which has : 2 Go RAM memory and 4 Go swap.
Here is the result of vmstat -n command :
$ vmstat -n
VM
memory page faults
avm free re at pi po fr de sr in sy ... (5 Replies)