IDS Forum

Re: Red Hat / Suse / Informix 10 / 2 Gb

Posted By: Andreas Breitfeld
Date: Friday, 20 April 2007, at 9:54 a.m.

In Response To: Red Hat / Suse / Informix 10 / 2 Gb (André Luiz Rufino)

Take a look to Linux Kernel 2.6.x configuration. Shared Memory related
kernel parameters are defined in /proc/sys/kernel:

/proc/sys/kernel/shmmax
max size of a Shared Memory Segment in Byte
recommendation 2GB: 2147483648

/proc/sys/kernel/shmall
total sum of Shared Memory in 4kB Pages
recommendation for 16GB Memory: 4194304

/proc/sys/kernel/shmmni
total sum of Shared Memory Segments
recommendation (Linux default): 4096

cat /proc/sys/kernel/<parameter>
Example:
cat /proc/sys/kernel/shmmax

Set values of kernel parameter dynamically:
echo <value> > /proc/sys/kernel/<parameter>
Example:
echo 2147483648 > /proc/sys/kernel/shmmax

Set values permanent in /etc/sysctl.conf
kernel.<parameter> = <value>
Example:
kernel.shmmax = 2147483648

32bit Linux (i686) limits the Virtual Memory of 4GB to 3GB for one
application. The rest of 1GB is reserved for the kernel. An exception
is the optional hugemem kernel of RHEL 4: 4GB Virtual Memory is
addressable.

64bit Linux (x86_64) is able to address almost 512GB (RHEL 4) or
131072GB (SLES 10) Virtual Memory.

The amount of Virtual Memory addressable as Shared Memory is restricted
by Binaries (Text und Heap), Shared Libraries and Stack. They are
located at different regions on different Linux distributions. The used
regions can be checked in file /proc/<ProcessID>/maps of a given
process, e.g.:
- detect ProcessID (pid #) of CPU VP (class cpu): onstat -g glo

vp pid class usercpu syscpu total
1 18303 cpu 3.48 0.20 3.68

- list regions (maps) of Virtual Memory: cat /proc/18303/maps

IDS Shared Memory requires one big, continuous (not interrupted) free
region in the Virtual Memory. The starting address of this region is
defined in ONCONFIG parameter SHMBASE.

RHEL 4 (i686)
-------------
Virtual Memory: 0x00000000 - 0xbfffffff
Shared Libraries: 0x00000000 ->
Binaries: 0x08000000 ->
Stack: <- 0xbfffffff
free space: 0x10000000 - 0xafffffff
SHMBASE 0x10000000L # provides 2,5GB Shared Memory
Using UDRs and Datablades loads Shared Libraries at Adress 0x00000000
ascending. Change of SHMBASE 0x10000000L may be required, e.g. to
0x40000000L

RHEL 4 (i686), hugemem Kernel
-----------------------------
Virtual Memory: 0x00000000 - 0xffffffff
Shared Libraries: 0x00000000 ->
Binaries: 0x08000000 ->
Stack: <- 0xffffffff
free space: 0x10000000 - 0xefffffff
SHMBASE 0x10000000L # provides 3,5GB Shared Memory
Using UDRs and Datablades loads Shared Libraries at Adress 0x00000000
ascending. Change to a higher value of SHMBASE 0x10000000L may be
required.

SLES 10 (i686)
--------------
Virtual Memory: 0x00000000 - 0xbfffffff
Binaries: 0x08000000 ->
Shared Libraries: <- 0xb7ffffff
Stack: <- 0xbfffffff
free Space: 0x10000000 - 0xafffffff
SHMBASE 0x10000000L # provides 2,5GB Shared Memory

Shared Libraries are loaded at address 0xb7ffffff descending .
Collisions of IDS Shared Memory Segments with Shared Libraries must be
avoided.

RHEL 4 (x86_64)
---------------
Virtual Memory: 0x0000000000 - 0x7fbfffffff
Binaries: 0x0000000000 ->
Shared Libraries: 0x2a95556000 ->

0x322ee00000 ->
Stack: <- 0x7fbfffffff
Big free spaces: 0x0010000000 - 0x2a8fffffff

0x3240000000 - 0x7fafffffff
SHMBASE 0x0010000000L # provides 170GB Shared Memory
SHMBASE 0x3240000000L # provides 309GB Shared Memory

Shared Libraries in the example are loaded at address 0x322ee00000
ascending. A higher value of SHMBASE 0x3240000000L may be required.

SLES 10 (x86_64)
----------------
Virtual Memory: 0x000000000000 - 0x7fffffffffff
Binaries: 0x000000000000 ->
Shared Libraries: 0x2a0000000000 ->
Stack: <- 0x7fffffffffff
Big free spaces: 0x000010000000 - 0x29ffffffffff

0x2c0000000000 - 0x7fffa0000000
SHMBASE 0x000010000000L # provides 43000GB Shared Memory
SHMBASE 0x2c0000000000L # provides 86000GB Shared Memory

Shared Libraries are loaded at address 0x2a0000000000 ascending. A
higher value of SHMBASE 0x2c0000000000L may be required.

Andreas

On Thursday 19 April 2007 15:21, André Luiz Rufino wrote:
> Hi folks,
>
> I´m trying to wake up a informix instance on SUSE ( and Red Hat too
> ). They are 32 BITS OS both. Is there a memory alocation limit to
> those plataforms? May I use more than 2 Gb in my shared memory
> alocation?
>
> Thanks,
>
> André Luiz
> _________________________________________________________________
> Veja só alguns dos novos serviços online no Windows Live Ideas —
> são tão novos que ainda não foram disponibilizados oficialmente.
> http://ideas.live.com
>
>
> *********************************************************************
>********** Forum Note: Use "Reply" to post a response in the
> discussion forum.

--
Andreas Breitfeld; Informix Development Munich
IBM Deutschland GmbH; Vorsitzender des Aufsichtsrats: Hans Ulrich
Maerki; Geschäftsführung: Martin Jetter (Vorsitzender), Rudolf Bauer,
Christian Diedrich, Christoph Grandpierre, Matthias Hartmann, Andreas
Kerstan; Sitz der Gesellschaft: Stuttgart; Registergericht: Amtsgericht
Stuttgart, HRB 14562; WEEE-Reg.-Nr. DE 99369940

Messages In This Thread

• Red Hat / Suse / Informix 10 / 2 Gb
  André Luiz Rufino -- Thursday, 19 April 2007, at 9:21 a.m.
  • RE: Red Hat / Suse / Informix 10 / 2 Gb
    Jarratt, Linwood B. -- Thursday, 19 April 2007, at 10:30 a.m.
  • Re: Red Hat / Suse / Informix 10 / 2 Gb
    Andreas Breitfeld -- Friday, 20 April 2007, at 9:54 a.m.

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