Re: Hugepages - benefits / drawbacks

To my understanding Oracle 10.2 on Solaris 10 can use 4M pages without any SA intervention 8-):

# pmap -xs 12211 | grep ism
0000000380000000 77824 77824 - 77824 4M rwxsR [ ism shmid=0x24 ]
00000003C0000000 98304 98304 - 98304 4M rwxsR [ ism shmid=0x25 ]
0000000400000000 90112 90112 - 90112 4M rwxsR [ ism shmid=0x26 ]
0000000440000000 8 8 - 8 8K rwxsR [ ism shmid=0x27 ]
And PGA pagesize is controlled by underscore parameter David mentioned before.

--romas

On Thu, Oct 9, 2008 at 2:25 PM, Bort, Guillermo <guillermo.bort_at_eds.com>wrote:

> Does anyone have any doc (for the Unix SA) for hugepages on Solaris
> 9/10?
> so I can get their help to implement this?
>
> TIA
>
> Guillermo Alan Bort
> DBA / DBA Main Team
>
> EDS, an HP company
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Yong Huang
> Sent: Thursday, October 09, 2008 1:31 PM
> To: oracle-l_at_freelists.org
> Cc: David.J.Miller_at_Sun.COM; roman.podshivalov_at_gmail.com
> Subject: Re: Hugepages - benefits / drawbacks
>
> Thanks, David. That finally anwers my (and maybe Roman's) question: How
> can ISM be used for PGA? Just because there's a shared (or rather,
> sharable) memory segment created doesn't mean it must be shared. Solaris
> ISM or Linux HugePages is just a name for this technology. It has all
> these features: (a) sharing page tables between processes, (b) large
> memory page size, (c) locking pages in memory (related to (a)). The name
> ISM emphasizes (a), while HugePages emphasizes (b). The Oracle parameter
> _use_ism_for_pga confused me simply because they used the term ism in
> it. If it was called _use_largepage_for_pga without any change in its
> implementation, I wouldn't ask the question.
>
> Yong Huang
>
> > From: David Miller <David.J.Miller_at_Sun.COM>
> >
> > Hi Roman,
> >
> > ISM is indeed shared memory, but it is possible to allocate it and
> only
> > use it in one place, i.e. a single process's PGA. Once it's mapped
> into
> > the address space, it's just memory (at least mostly). Clearly when
> > this was implemented, the PGA for each process would use a different
> > shared memory segment so there wouldn't be collisions.
> >
> > As I mentioned before, I'm sure it was done to use large pages. Since
> there
> > are other mechanisms now, it's no longer necessary, which is why it
> was
> > obsoleted in 10.2.
> >
> > Regards,
> >
> > Dave
> >
> > Roman Podshivalov wrote, On 10/07/08 18:30:
> > > David,
> > >
> > > In my mind ISM is related to shared memory, could it be used for
> private
> > > memory allocation ?
> > >
> > > thanks
> > > --romas
>
>
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

--
http://www.freelists.org/webpage/oracle-l