Regarding AIX Memory Utilization usage calculation


 
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Operating Systems AIX Regarding AIX Memory Utilization usage calculation
# 8  
Old 03-13-2013
Yes, pinned means out of the pool of dynamically mapped pages. They can be shared or not depending on what they are! Oracle is paranoid, or doing a lot of I/O. If you use it you will not lose it!
# 9  
Old 03-14-2013
Quote:
Originally Posted by DGPickett
Yes, good old shared memory is used by the traditional UNIX IPCs, including semaphores and queues. I am not sure why these have to be pinned. Pinning is usually for peripheral/I/O support or the paranoid.

You can do similar things without shared memory or pinning using mmap() and files. An area of a file can be mmap()'d by all related processes, no root required. The content is durable through boots, too!
Guess I need to write a program to find out definitely what system calls are being used to share memory segments on AIX.
IIRC (if I recall correctly) - shmap()/mmap() - pins a file to memory. And misuse by applications can have a tremendous impact on memory management. And "way back when - AIX 4.1.4 and 4.1.5 if I recall, shmap()/mmap() were null operations on AIX (for POSIX they only need(ed) to be defined ("standards guy" might verify this) - i.e., there was/is no implementation definition. And why a null operation? Because AIX was already caching files in memory by default.
Note: currently (since a patch in AIX 4.2 or 4.3) expected shmap/mmap behavior is implemented in AIX - so also since "way back...".

Again, on AIX - the preferred tool for memory analysis is svmon.
# 10  
Old 03-14-2013
I see many systems have a malloc option that is mmap() based (uses no swap, but sometimes temp files are on /tmp and so is swap!). Later Solaris uses mmap() on FILE* input for flat files -- no buffer. I'd like to see C/C++ APIs for no-root semaphores and better queues like MQ, TIB in mmap(). I suppose JMS is there already.

It seems like mmap() is too little studied. It is the door to an additional dimension in application resources -- control of your own VM. With it, you can exploit whatever RAM is available in a small program. Now if I could just reposition pages in files without data area read-write. I suppose the disk defrafmenter will just do the read-write later! That's IT life! You think you have an interrupt, but down in the kernel someone else is polling.
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