topic Re: maxssize Syntax in Operating System - HP-UX

maxssize Syntax

DareDevil_1 — Fri, 07 Sep 2007 05:04:54 GMT

hi,

please let me know how to set the maxssize at user level or is it advisable to change it at kernel level??

read in a HP doc tht its better to define maxssize in the application.

Re: maxssize Syntax

Steven E. Protter — Fri, 07 Sep 2007 05:35:34 GMT

Shalom,

maxssiz is a kernel parameter. It can not be set by a user, only root.

kctune to see if root can set it dynamically.

SEP

Re: maxssize Syntax

AwadheshPandey — Fri, 07 Sep 2007 05:54:37 GMT

maxssize can be set by root only and normal user can not change this parameter. value of maxssize should set as required by application.

Re: maxssize Syntax

DareDevil_1 — Fri, 07 Sep 2007 06:10:39 GMT

thanks for your timely response.please tell me what they mean in this doc,

http://docs.hp.com/en/B2355-60105/maxssiz.5.html

Re: maxssize Syntax

Wim Rombauts — Fri, 07 Sep 2007 06:18:31 GMT

The doucment is about the maxssiz, maxssiz_64bit kernel parameters.

A said in above entries, they can only be set at system level by root.

The more inmportant question is : why do you want to change it ? Did you receive application errors, or software documentation to increase the parameter ?

Re: maxssize Syntax

DareDevil_1 — Fri, 07 Sep 2007 06:44:53 GMT

hi,

reason for changing: one day suddenly the application we are running on that server crashed for no reason and wont come up coz stack size is less.would reboot of the server help?

Re: maxssize Syntax

Wim Rombauts — Fri, 07 Sep 2007 06:56:03 GMT

Yes, a reboot can help, but maybe it won't.
It doesn't hurt to increase maxssiz or maxssiz64 (but don't increase too much, ad 25% or so), but you should find the cause of the problem : Why does it suddenly need more stack size while it has been running fine for so long ?

Re: maxssize Syntax

A. Clay Stephenson — Fri, 07 Sep 2007 09:20:39 GMT

First of all, the default ulimit (8MiB) can be a bit small so your probably do want to increase the kernel tunable, maxssiz, up to something like 32-64MiB. Even the 64-bit counterpart, maxssiz_64bit very seldom needs to be larger than about 128MiB --- and that is very generous. Well written code almost never needs stacks any larger than this; if you find that you do need stacks larger than these values then almost certainly the code is badly written --- although there could be exceptions (e.g. intentionally, highly recursive algorithms). Most often when larger stacks than ~ 32-64MiB are needed, you are fixing the symptoms rather than fixing the problem --- bad code. If you have set you stack size up to 32-64MiB and you need larger ones for a few applications then one way to have you cake and eat it too is to set maxssiz to some larger value. This will be a global value. You can then use ulimit -S s smaller_value to reduce the stack for users on an individual basis in their .profiles --- or a file sourced by their .profiles.

One major drawback to a larger stack size -- especially for 32-bit applications -- is that the stack and data segment are allocated from the same quadrant. This means that however large you make maxssiz, you reduce the data segment by that much -- even if the run-time stack never approaches the limit.