memory allocation

[moonchild]

What are the limitations the OS has on allocating memory to an application-

Is there a limitation (ex. if you had 4 Gig, or 16 Gig base memory) ?

[Mel Burslan · Accepted solution]

I am assuming you are talking about the data size allocated for the application. You can see how much space is allocated for the user which is logged in under by running the command

ulimit -a

for more information on usage of memory, you can find many discussions from earlier times on the subject by making an advanced search on forums. One from my favorite links is here :

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=902772

Hope this helps

[Victor Fridyev]

Hi,

Look at the http://docs.hp.com/en/939/KCParms/KCparams.OverviewAll.html

Look at maxdsiz parameter

HTH

[A. Clay Stephenson]

You essentially have two limits and the amount of physical has nothing to do with it. 1) The maximum size of the data segment which is determined by the kernel tunable maxdsiz (or maxdsiz_64bit for a 64-bit application). There are some more "gotcha's" especially with 32-bit applications. Unless some special linker options are used, the data segment can be no larger than 1 quadrant -- which for 32-bit applications is 1GiB. Also, maxssiz also sunbtracts from this available pool. 2) The total virtual address space which is determined by the amount of swap space available.

Now the amount of physical memory will have enormous impact upon how well the application will run but not directly upon the limits to which it can allocate memory.

To add to the confusion, HP-UX also has something called pseudoswap (which isn't swap) but allows 75% of the physical memory to be used in the VAS calculation. It is really only intended for boxes which have much more memory than swap space.