RE: 11g RedHat 5 and Hugepages
- From: "Crisler, Jon" <Jon.Crisler@xxxxxxx>
- To: <ora_kclosson@xxxxxxxxx>, <Oracle-L@xxxxxxxxxxxxx>
- Date: Wed, 13 Oct 2010 11:06:30 -0400
In my case, I am looking at a connection count of at least 5000, with an
SGA of 70gb or higher, on each node of a 6 node cluster, with each node
having 48 cpu's. We have run into issues with MTS and will be using
dedicated connections on the DB side but the numerous app servers have
connection pooling. The database size will be about 6 TB to start.
Preliminary testing on a small system already showed a performance gain
when using hugepages, but the test was on SUSE Linux while we are using
RedHat 5, so its not a 100% accurate comparision.
This 6 node cluster will replicate to an identical cluster with
DataGuard.
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
<ora_kclosson@xxxxxxxxx>
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
memory
handling for 32-bit Windows. Not even sure if that one is handled with a
TLB,
looks like the old PC Expanded memory?
Systems with large connection counts nowadays are handled with pooled
connections
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
use
hugepages with 64-bit OS's. No doubt whatsoever in my mind it has an
advantage
for the larger SGA sizes so common in those. In fact, I'm continually
surprised
it's not a default setup for Oracle in 64-bit OS's!
Cheers
Nuno
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
the
wasted page table memory.
>
>Use hugepages.
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