[SunHELP] Solaris 2.6 Memory Limitation
Josh McCormick
sunhelp at sunhelp.org
Wed Feb 28 16:08:31 CST 2001
Naser Ali wrote:
> But on the other hand the Solaris 2.6 or earlier versions are 32 bit
> as well. Therefore, theoretically/technically they should not be able
> to address more than 4 gig. In your case you have 10 gig on your E10k,
> which means the 6 gig of it is never used or addressed by the OS.
> Solaris would only create page segments of 8k upto 4 gig at startup.
Well, I think the distinction is more that 32 bit Solaris can only give
a process a virtual memory space up to 4gb. However, since you have
multiple processes, and each process can have its own virtual memory
space (and the kernel, too), it allows it to use the 10gb of physical
address space.
Put another way, a segment of memory used by a process has a starting
address. This starting address is not limited by 32 bits and can go into
obscenely high numbers. So, a process could start at the 8gb mark in
memory. No big deal. However, the size of an address space IS 32 bits,
and therefore, can only allocate memory segments up to 4gb. *
So, you can have processes that their starting point in memory is
anywhere in physical memory, it is just their length of how far each
segment can go that is limited.
* - This isn't *quite* true because of page mapings and what not, but
the general idea is correct. The operating system is capable of letting
processes go anywhere in memory, well beyond 64gb. However, the
limitation is on how big a chunk of memory a single process can take.
> Correct me I am wrong, any one ...?
> Thanks
>
> -----Original Message-----
> From: Josh McCormick [mailto:josh.mccormick at wcom.com]
> Sent: Wednesday, February 28, 2001 2:34 PM
> To: sunhelp at sunhelp.org
> Subject: Re: [SunHELP] Solaris 2.6 Memory Limitation
>
> I've got a number of E10k domains running 2.5.1 and 2.6. One in
> particular I'm looking at has 10gb of RAM. Yes, you can have greater
> than 4gb of memory and be able to access it.
>
> I think the catch, or the distinction here, is that a process, for
> example, Sybase or Oracle, cannot grab a block bigger than 4gb by
> itself. However, the combination of all the processes running on your
> system can go well beyond 4gb.
>
> Actually, I've run into this, in that we wanted to increase the shared
>
> memory pool that Sybase uses for caching. But the operating system
> limits the amount that an instance of Sybase can grab to 4gb. However,
>
> there are a number of other things that run on that system in addition
>
> to sybase, and it consumes around 11gb of memory (with swap devices
> holding the excess 1gb).
>
> Hope this explains things.
>
> "Fletcher, Joe" wrote:
> >
> > In something like an E10K you can split the >4Gb into domains and
> allocate a
> > chunk for each domain.
> >
> > -----Original Message-----
> > From: Mohammed, Ahsan [mailto:ahsan.mohammed at bankofamerica.com]
> > Sent: 28 February 2001 17:16
> > To: sunhelp at sunhelp.org
> > Subject: RE: [SunHELP] Solaris 2.6 Memory Limitation
> >
> > If it can address only 4GB what is the purpose of having more than
> 4GB?
> > I mean how can the remaining be put into use?
> > Thanks in Advance.
> > Ahsan
> >
> > Ahsan Mohammed
> > Database Administrator
> > (214) 209 2574
> > Pager: 877 677 5480
> >
> > -----Original Message-----
> > From: Fletcher, Joe [SMTP:joe.fletcher at metapack.com]
> > Sent: Wednesday, February 28, 2001 10:36 AM
> > To: 'sunhelp at sunhelp.org'
> > Subject: RE: [SunHELP] Solaris 2.6 Memory Limitation
> >
> > It's true that 32bit systems can only address a maximum of
> 4GB of
> > memory. That's not to say that a system running a 32bit o/s
> > can physically contain only 4GB RAM. Solaris 2.6 is 32bit
> therefore
> > it can only address up to 4GB.
> >
> > -----Original Message-----
> > From: Naser Ali [mailto:Ali.Naser at irs.gov]
> > Sent: 28 February 2001 15:23
> > To: sunhelp at sunhelp.org
> > Subject: [SunHELP] Solaris 2.6 Memory Limitation
> >
> >
> >
> > Hello Every one,
> > Just recently some one on our project mentioned that
> the
> > E10K we have which has 16Gig of memory running Solaris 2.6, has the
>
> > limitation of only 4 gig on the memory. Is that true with Solaris
> 2.6...?
> >
> > TIA
> >
> > MetaPack
> >
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> >
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> >
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> >
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> >
> > Fax: +44 (0) 20 7843 6721
> >
> >
> >
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