topic Re: Memory allocation limit in Operating System - HP-UX

Memory allocation limit

Gautam Shet — Mon, 08 Dec 2003 22:03:41 GMT

Hi folks,
I am experiencing an unusual problem in that, I cannot allocate memory of size ~ 67 MB on a machine having 512 MB main memory. I am using the standard C routine malloc() to allocate the memory. BTW this is a 32 bit application.

Could it be some system setting that has some limitation set to the memory allocation?. I would apperciate any pointers to resolve this problem.

Re: Memory allocation limit

Michael Tully — Mon, 08 Dec 2003 22:13:01 GMT

Have a look at this posting:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=210579

Re: Memory allocation limit

James Murtagh — Mon, 08 Dec 2003 23:21:49 GMT

Hi Gautam,

The problem will be kernel tunable maxdsiz for malloc requests for 32bit processes. You haven't mentioned the OS but the default on 10.20 and 11.00 is 67MB, defined in /usr/conf/master.d/core-hpux ;

# grep MAXDSIZ core-hpux
maxdsiz MAXDSIZ 0x04000000
# echo 0x04000000=D|adb
67108864

On 11i the default is raised to 256MB.

Cheers,

James.

Re: Memory allocation limit

Elmar P. Kolkman — Tue, 09 Dec 2003 03:16:31 GMT

It is 67 million bytes, which is in fact 64 Megabyte, depending on what you think of as Megabyte. In computer terms it is 1024 * 1024 bytes, while a lot of HD vendors think of Mb as 1000*1000 bytes...

So do a grep of maxdsiz in /stand/system. If it is not there, your limit is probably 64Mb (or 67108864) and you should start sam to change it if you are allowed to.

Re: Memory allocation limit

Gautam Shet — Wed, 10 Dec 2003 14:06:34 GMT

Hi folks,
Thanks for all your replies. Once I increased the value of maxdsiz to 256MB, using sam, the memory allocation went through fine.