Re: Hugepages - benefits / drawbacks
- From: "Roman Podshivalov" <roman.podshivalov@xxxxxxxxx>
- To: yong321@xxxxxxxxx
- Date: Tue, 7 Oct 2008 18:19:33 -0400
Not a problem at all.
I tested this with various statements and verified pga allocation via
v$sesstat view. Still I'm failing to understand the following logic. If
something is using ISM that means something is somehow involved with shared
memory segments, because ISM is nothing else but a different way of
controlling and allocating shared segments. If any operation creates shared
memory segment with or without ISM I should be able to observe it via ipcs
command output. So far under Solaris ipcs output matches with allocated SGA,
nothing else. And segment sizes are pretty static. Please point me out where
this logic is failing.
--romas
On Tue, Oct 7, 2008 at 4:53 PM, Yong Huang <yong321@xxxxxxxxx> wrote:
> Thanks Roman for the test.
>
> BTW, I was wrong in throwing the SQL for a big "sort":
> select count(*) from dba_source order by 1
> Sort Aggregate operation such as count(*) doesn't really sort. To sort and
> avoid big output, this SQL should work:
> with x as (select * from dba_source order by 1) select count(*) from x;
>
> Yong Huang
>
>
> --- On Tue, 10/7/08, Roman Podshivalov <roman.podshivalov@xxxxxxxxx>
> wrote:
>
> > From: Roman Podshivalov <roman.podshivalov@xxxxxxxxx>
> > Subject: Re: Hugepages - benefits / drawbacks
> > To: yong321@xxxxxxxxx
> > Cc: "Christo Kutrovsky" <kutrovsky.oracle@xxxxxxxxx>,
> oracle-l@xxxxxxxxxxxxx, krishmanoh@xxxxxxxxx
> > Date: Tuesday, October 7, 2008, 3:30 PM
> >
> > With default setting of _use_ism_for_pga set to TRUE - no
> > changes in shared
> > memory segments (pmap -s/pmap -x) were observed during
> > sorting operation.
> > Speaking of mmap/brk calls - no such calls happened _during
> > the sort_
> > according to truss output. Looks like PGA is not using ISM
> > despite the
> > underscore parameter 8-). Oracle 10.2.0.3, Solaris 10.
> >
> > --romas
> >
> > On Tue, Oct 7, 2008 at 3:08 PM, Yong Huang
> > <yong321@xxxxxxxxx> wrote:
> >
> > > ipcs probably won't show anything interesting. Can
> > you check truss output
> > > when you do a big sort (select count(*) from
> > dba_source order by 1)? Filter
> > > on calls such as brk, mmap (get args of this). Also
> > pmap -x | grep shmid.
> > > See if the mapped size increases when you do big
> > sorting. And, pmap -s <your
> > > shadow process> to see which page size segment
> > increases its size.
> > >
> > > Yong Huang
> > >
> > >
> > > --- On Tue, 10/7/08, Roman Podshivalov
> > <roman.podshivalov@xxxxxxxxx>
> > > wrote:
> > >
> > > > From: Roman Podshivalov
> > <roman.podshivalov@xxxxxxxxx>
> > > > Subject: Re: Hugepages - benefits / drawbacks
> > > > To: yong321@xxxxxxxxx
> > > > Cc: "Christo Kutrovsky"
> > <kutrovsky.oracle@xxxxxxxxx>,
> > > oracle-l@xxxxxxxxxxxxx, krishmanoh@xxxxxxxxx
> > > > Date: Tuesday, October 7, 2008, 1:59 PM
> > > >
> > > > Yep that parameter caught my attention too. I
> > just did a
> > > > quick test and
> > > > started database with this parameter set to true
> > and false.
> > > > No difference in
> > > > ipcs -ma output was found....Could that be
> > related to MTS
> > > > configuration ?
> > > >
> > > > --romas
> > > >
> > > > On Tue, Oct 7, 2008 at 2:55 PM, Yong Huang
> > > > <yong321@xxxxxxxxx> wrote:
> > > >
> > > > > > On Tue, Oct 7, 2008 at 1:26 PM, Yong
> > Huang
> > > > > > <yong321@xxxxxxxxx> wrote:
> > > > > > > Hi Krishna,
> > > > > > >
> > > > > > >> on Solaris PGA uses ISM
> > > > > > >
> > > > > > > Wouldn't that cause PGA to be
> > shared?
> > > > >
> > > > > Tanel Poder's presentation "Memory
> > Management
> > > > and Latching Improvements in
> > > > > Oracle9i and 10g" mentions the
> > parameter
> > > > _use_ism_for_pga. It didn't
> > > > > register in my mind when I read it some time
> > ago. I
> > > > don't have access to
> > > > > Oracle on Solaris right now. Why does Oracle
> > do this?
> > > > It would be
> > > > > interesting to see the effect.
> > > > >
> > > > > Yong Huang
>
>
>
>
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