Kernel Parameter maxsiz and maxsiz_64bit to increase. !

[rveri]

Hi All ,

I got a request from the application owner to increase this the parameters:
(maxdsiz and maxdsiz_64bit )

# kmtune -q maxdsiz
Parameter Current Dyn Planned Module Version
===============================================================================
maxdsiz 1073741824 - 1073741824

root@ddmph17 [/]
# kmtune -q maxdsiz_64bit
Parameter Current Dyn Planned Module Version
===============================================================================
maxdsiz_64bit 0x80000000 - 0X80000000

-----------------------------------------
OS = B.11.11 U 9000/800
------------------------------------------
Just wanted to know ,

i)what are the things I need to know related to this , I am aware of that it will take a reboot for this.

ii) What this parameters do .

Thanks ,
Veri.

[Pete Randall]

maxdsiz and it's 64bit version, maxdsiz_64bit set the maximum stack segment size for programs - the limit for how much data they can load.


Pete

[RAC_1]

the maxdsiz is size for data segment. The maxdsiz_64bit is for 64 bit progrms. you value is 1.07GB, why applications owners want to increase it. you already have set it generously.

[Steven E. Protter]

cd /stand

kmtune -s maxdsiz_64bit

Doesn't have to be hex

Same procedure for maxdsiz


# might want to back up the system file.

mk_kernel

cp vmunix vmunix.prev

boot the box.

SEP

[Alex Lavrov.]

It's probably maxdsiz_64bit, since you probably havce 64bit processor and it's set to 2GB.

0x80000000 = 2GB

It a pretty big value and I wonder what application can demand more than 2GB ...

Alex.

[Bill Hassell · Accepted solution]

As mentioned, these two parameters limit the maximum size for data inside a program There are no penalties or interactions with these parameters EXCEPT maxdsiz_64 must be larger than maxdsiz. You could set maxdsiz to 1800 megs and maxdsiz_64 to 4000 megs to give the users lots of room. If the developers run into memory problems, there are many referemces here in the forums concerning the limitations of 32bit programs and large memory limitations. Here is a start:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=955459

[rveri]

i) How you all are calculating ,
maxdsiz_64bit is = 0x80000000 = 2GB. (any formula !)

ii) And how much physical memory it is going to occupy if I make it double , that is upto 4GB , I am having 4GB Phy. Memory.

iii) And what will be the (kmtune )value for setting it 4GB ,

many thx.
veri.

[Rajesh SB]

Hi,

maxdsiz parameter: is Max Data Segment Size For 32-bit Processes (Bytes)

Where as
maxdsiz_64bit: Max Data Segment Size For 64-bit Processes (Bytes)

Maxdsiz defines the maximum size of the data segment of a process. The default value of is too small for most applications. We recommend this value be set to the maximum value. If maxdsiz is exceeded, the process will be terminated, usually with a SIGSEGV (segmentation violation) and you will probably see the following message:

Memory fault(coredump)
In this case, review the values of maxdsiz, maxssiz and maxtsiz. For more information on these parameters, please see the on-line Help section within SAM's Kernel Configuration. If you need to exceed the specified maximum of 1.9Gb, there are a couple of ways (yet to be supported) to do so. Contact your Hewlett Packard technical consultant for the details. It is important to note that the maxdsiz parameter must be modified in order for these procedures to work. Maxdsiz will need to be set to 2.75Gb or 3.6Gb depending on the method chosen and/or size required. It will also require a manual creation of a new kernel.


Regards,
Rajesh

[rveri]

got idea. thanks all.