Is a shared memory segment contiguous?

Is a shared memory segment contiguous?

Post by jc » Sat, 02 Feb 2002 11:24:20



        Greetings,
I was wondering if Solaris 2.7/8 treat shared memory contiguously.  I know
Oracle uses shared memory segments, and I was curious if that segment is
mapped contiguously from physical memory or if the OS just grabs chunks of
memroy to form the segment.  I hope I am being clear here as I am not 100%
on how Solaris handles all the memory management.

tks

jc

JC

 
 
 

Is a shared memory segment contiguous?

Post by Rich Tee » Sat, 02 Feb 2002 12:42:03



> I was wondering if Solaris 2.7/8 treat shared memory contiguously.  I know
> Oracle uses shared memory segments, and I was curious if that segment is
> mapped contiguously from physical memory or if the OS just grabs chunks of
> memroy to form the segment.  I hope I am being clear here as I am not 100%
> on how Solaris handles all the memory management.

I don't think there's a way of knowing, but why would you care?
The virtual memory will be contiguous, but there's no guarantee
that the physical memory will be.  Heck, there's no guarantee
that all the pages will be in memory anyway!

In short: I can't see why it would matter.  All userland memory
accesses are in virtual memory, not physical.

--
Rich Teer

President,
Rite Online Inc.

Voice: +1 (250) 979-1638
URL: http://www.rite-online.net

 
 
 

Is a shared memory segment contiguous?

Post by J » Sun, 03 Feb 2002 00:14:27




> > I was wondering if Solaris 2.7/8 treat shared memory contiguously.  I know
> > Oracle uses shared memory segments, and I was curious if that segment is
> > mapped contiguously from physical memory or if the OS just grabs chunks of
> > memroy to form the segment.  I hope I am being clear here as I am not 100%
> > on how Solaris handles all the memory management.

> I don't think there's a way of knowing, but why would you care?
> The virtual memory will be contiguous, but there's no guarantee
> that the physical memory will be.  Heck, there's no guarantee
> that all the pages will be in memory anyway!

> In short: I can't see why it would matter.  All userland memory
> accesses are in virtual memory, not physical.

I only asked bc some Linux Oracle dba came over to my cube and was
touting that Linux would grab chunks of memory for its shared memory
segment under Linux, I then realized I didnt know how Solaris handled
it, but I did realize it was trivial.

As usual for the reply!

jc