Re: Using AMM with Linux RAC
- From: Thomas Roach <troach@xxxxxxxxx>
- To: tanel@xxxxxxxxxx
- Date: Thu, 18 Feb 2010 12:00:01 -0500
Tanel,
Is it possible for Oracle to eventually have AMM and hugepages support?
I think I recall some blog posts by Kevin Closson on this topic and I don't
recall if it was a limitation with the memory being able to dynamically
resize and hugepages not supporting that?
Thanks,
Tom
On Thu, Feb 18, 2010 at 11:02 AM, Tanel Poder <tanel@xxxxxxxxxx> wrote:
> Hi Sherrie,
>
> The memory which is reserved for PGA_AGGREGATE_TARGET will not show up in
> /dev/shm as it's not shared (PGAs are still allocated using process-private
> memory).
>
> You can query V$MEMORY_DYNAMIC_COMPONENTS to see how Oracle is currently
> using the memory:
>
> SQL> select component, current_size from v$memory_dynamic_components where
> component like '%Target%';
>
> COMPONENT CURRENT_SIZE
> ------------------------------ ------------
> SGA Target 545259520
> PGA Target 293601280
>
>
> Note that hugepages are not used with AMM on Linux so you may be not
> getting all the performance out of your hardware...
>
> --
> Tanel Poder
> http://tech.e2sn.com
> http://blog.tanelpoder.com
>
>
> On Thu, Feb 18, 2010 at 9:51 PM, Sherrie Kubis <
> Sherrie.Kubis@xxxxxxxxxxxxxxxxxx> wrote:
>
>> We have a 3-node (each 32 gb ram) Linux RAC cluster running Oracle
>> 11.1.0.7, housing 4 instances with a total memory_target of 8.75 gb. OEM
>> shows 29% ram is used. We are using AMM.
>>
>>
>>
>> The free -mt command shows:
>>
>>
>>
>> total used free shared buffers cached
>>
>> Mem: 32189 31519 669 0 1250 25168
>>
>> -/+ buffers/cache: 5101 27088
>>
>> Swap: 32767 39 32728
>>
>> Total: 64957 31559 33397
>>
>>
>>
>> It looks like tmpfs is 16gb:
>>
>> df -k /dev/shm
>>
>> Filesystem 1K-blocks Used Available Use% Mounted on
>>
>> tmpfs 16481056 5604532 10876524 35% /dev/shm
>>
>>
>>
>> We are seeing 5.6gb of memory used, so I'm confused about why the SGAs are
>> defined to consume 8.75gb, but we only see 5.6gb used. I read that the SGA,
>> by default, takes 60% of memory_target and pga gets the rest. Because there
>> are not yet many connections, is this why we see a lower value?
>>
>>
>>
>> Does the tmpfs at 16gb mean we can only use 16gb of ram for our databases?
>>
>>
>>
>> Any insights would be appreciated. We are just starting out with Linux
>> and Posix-Style shared memory management, quite different than shared
>> semaphore memory segments that we were used to.
>>
>>
>>
>> *Sherrie Kubis *
>>
>> Southwest Florida Water Management District
>>
>>
>>
>>
>>
>>
>>
>> IMPORTANT NOTICE: All E-mail sent to or from this address are public record
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>>
>
--
Thomas Roach
813-404-6066
troach@xxxxxxxxx
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