Re: [Linux-ia64] Kernel Shared Memory Max (shmmax)

> And based on that the total amount of shared memory segment
> that can be created in IA-64 platform (with 16K page size) is 8G.

Does this still hold true in newer kernel releases (since 03/2002)?  Is 8G the 
max for IA64 kernel?

Thanks,
Donny

On Thu March 14 2002 5:13 pm, Seth, Rohit wrote:
> shmmax is the size of largest shared memory (in bytes) segment that the
> kernel allows.  System wide value of total shared memory value is given by
> shmall parameter.  Currently the default value for shmmax is  (extrememly
> low) 32MB.  And based on that the total amount of shared memory segment
> that can be created in IA-64 platform (with 16K page size) is 8G. There is
> no direct relationship between shmmax value and the amount of physical
> memory available in the system.  Though you will never be able to create a
> shared memory segment bigger then the total memory (Free RAM+Free SWAP)
> available on the machine (unless you change the sysctl_overcommit_memory).
> Besides that, this low default value of 32MB just adds overhead for big
> memory systems.  It will be nice to change this default value to 2G at
> least for IA-64 machines.
>
> You can also change this value of shm* (shmmax etc.) by writing proper
> values in /proc/sys/kernel/shm*
>
> rohit
>
> -----Original Message-----
> From: Donny Cooper [mailto:[email protected]]
> Sent: Thursday, March 14, 2002 2:40 PM
> To: [email protected]; [email protected]
> Subject: [Linux-ia64] Kernel Shared Memory Max (shmmax)
>
>
>
> Does the maximum possible shared memory (shmmax) increase with the
> Enterprise kernel?
>
> Below is from doc/sysctl/kernel.txt document.
> Is this document valid for IA-64 kernel?
>
> It seems you can set this value to pretty much anything (even larger than
> the available memory), so I'm assuming the
> value gets intelligently truncated to the max supported.  How can I check
> how much shared mem is available, `free` or
> `top` just shows what's used, right?
>
> ...doc/sysctl/kernel.txt
> ==============================================================
>
> shmmax:
>
> This value can be used to query and set the run time limit
> on the maximum shared memory segment size that can be created.
> Shared memory segments up to 1Gb are now supported in the
> kernel.  This value defaults to SHMMAX.
>
> ==============================================================
>
>
> Thanks,
> -----------------------------------
> Donny Cooper
> NEC Systems, Inc.
> Advanced Technical Computing Center
> [email protected]
> -----------------------------------
>
>
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-- 
=================================
	     Donny Cooper
      NEC Solutions (America), Inc.
Advanced Technical Computing Center
	 ph: +1-281-465-1506
     [email protected]
=================================