Re: strange limit on shmmax on HP 32 bit

From: Robert Klute (robert_klute_removethis_at_hp.com)
Date: 07/25/03 

Date: Fri, 25 Jul 2003 09:53:06 -0700

On 25 Jul 2003 07:56:41 -0700, rguoussevdonskoi@metasolv.com (Roman
Guoussev-Donskoi) wrote:

>Please note the the in HPUX11i documentation on docs.hp.com as well as
> in my message specified restriction comes to 64M. They lost one zero
>when published it.
>HPUX shmmax:
>0x40000000 (11.0 docs.hp.com)
>0X4000000 (11.11 docs.hp.com)
>
>Nothing to do with 1G quadrants.

Actually, it does. You are right that the smaller number is a typo.
However, the largest single shared memory segment that can be allocated
on the 32-bit OS is 1 GByte, and it is because a quadrant is 1 GByte in
size. You can allocate upto 1.75 GB (2.75 if you use SHMEM_MAGIC), but
it requires multiple segments.

32-bit applications still have this restriction even on the 64-bit OS.

>
>Juan Paradinas Saenz de Viteri <n00990a@alcatel.es> wrote in message news:<3F1D1AB0.3052E8BF@alcatel.es>...
>> In a 32 bit OS a proccess can address up to 4 GB of memory. This space
>> address is splited in 4 scapes of 1 GB each: first for text, second for
>> data, and third and forth for shared memory and memory mapped files.
>> That's the reason.
>>
>> Regards
>>
>>
>> Roman Guoussev-Donskoi wrote:
>>
>> > Does anybody know why HP set maximum on shmmax to 0X4000000=67108864
>> > on 32 bit kernel? Does it not look extremely low even for 32 bit OS?

Robert Klute
Cupertino Solution Center
Hewlett-Packard Company
-----
The opinions are those of the poster, not the company.