RE: 11g RedHat 5 and Hugepages

  • From: "Crisler, Jon" <Jon.Crisler@xxxxxxx>
  • To: <ora_kclosson@xxxxxxxxx>, <Oracle-L@xxxxxxxxxxxxx>
  • Date: Wed, 13 Oct 2010 11:59:37 -0400

I was able to fix my hugepages issue.  It was caused by a number of
different things.


1)      Although SGA_MAX_SIZE and SGA_TARGET were set, there were both
_SGA parameters from autotuning, AND individual SID settings in the
spfile that were overriding my intended settings.  Same for
memory_target and memory_max_target.   Creating a pfile and carefully
reviewing it showed this problem- I felt pretty stupid for not doing
this sooner.

2)      Once I got past that issue, then I got ORA-27102 errors which
were caused by a SHMALL parameter set too small.  Easy to fix.

3)      I successfully tested without the /etc/sysctl.conf setting for
vm.hugetlb_shm_group - it is not needed in Red Hat assuming that the
limits.conf and ulimit settings are correct. 


I currently am running with 50gb in huge pages, which will probably get
bumped to 64 to 72gb once we start testing.   Thanks to all the
suggestions !!! It was nice to get so much help.


From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Kevin Closson
Sent: Wednesday, October 13, 2010 10:56 AM
To: Oracle-L@xxxxxxxxxxxxx
Subject: Re: 11g RedHat 5 and Hugepages


Nothing wrong with this feedback because it includes information about
how to do it right (e.g., pooled connections). But therein lies my
point. Take you 1GB SGA and attach a couple hundred dedicated connection
and you'll wish you'd have either a) used huge pages or b) reduced your
dedicated connection count. I wrote:

"Any system with large connection count is not going to be able to
afford the wasted page table memory."

So, while this is a good follow up it isn't disagreeing at all with what
I am said.

Oh, by the way, why on earth would anyone still be using a 32-bit OS?
That is a larger question.

In summary, if you don't like the size of the page tables do something
about it. 



From: "dbvision@xxxxxxxxxxxx" <dbvision@xxxxxxxxxxxx>
To: Jon.Crisler@xxxxxxx; tgascard@xxxxxxxxx; Kevin Closson
Cc: Oracle-L@xxxxxxxxxxxxx
Sent: Tue, October 12, 2010 11:31:39 PM
Subject: Re: 11g RedHat 5 and Hugepages

Beg to disagree there, Kevin.  Hugepage setup - in Linux, mind you - is
more a
hindrance than an advantage until one starts to talk about SGA sizes of
much more
than a couple GBs.  

Hardly possible in 32-bit OS's, where with luck one gets an SGA of 2GB,
if that.
Of course I'm not including things like Wintel's weird windowed large
handling for 32-bit Windows. Not even sure if that one is handled with a
looks like the old PC Expanded memory?

Systems with large connection counts nowadays are handled with pooled
in 99% of the cases. I've lost memory of the last application server
I've seen
that didn't use some form or other of that for large number of
connections.  And
there is always MTS/Shared connection/whatever-its-name-is-nowadays. :)

Don't get me wrong, though: I've been asking folks for a long time to
hugepages with 64-bit OS's.  No doubt whatsoever in my mind it has an
for the larger SGA sizes so common in those.  In fact, I'm continually
it's not a default setup for Oracle in 64-bit OS's!


On Wed Oct 13  2:26 , Kevin Closson  sent:

>Also, this notion that 32bit OS deployments don't need hugepages is
quite wrong.
Any system with large connection count is not going to be able to afford
wasted page table memory.
>Use hugepages.



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