Re: Numa Config Effekt in 19c?

Thanks Tanel

Am 23.06.2022 um 21:30 schrieb Tanel Poder:
> Worth saying that:
>
> 1) NUMA being a *hardware* topology thing, you can't turn NUMA on/off.
> If you have NUMA hardware, NUMA is always on :-)
>
> 2) You can turn NUMA-*awareness* on/off at OS level
>
> 3)  Additionally, you can turn NUMA-awareness on/of at Oracle level
>
> Turning NUMA awareness on at OS level makes the OS aware and do some
> of its memory/process placement in a NUMA aware mode, hopefully
> increasing performance. Some processes/memory pages can dynamically be
> /migrated/ to the NUMA node where they should reside (for better
> locality).
>
> That's great and exciting functionality for a performance geek, BUT
> this increases complexity and unexpected operations (on the memory you
> want to access), latency spikes etc.
>
> The same goes for the /additional /NUMA awareness & placement
> functionality at Oracle level. Even more complexity (and if you get
> unlucky, instability).
>
> If you have a modern 2-socket server (where remote memory access
> latency is not multiple /times/ higher than local), keep NUMA
> awareness off at OS and Oracle level). But, yeah with some (old?) 8
> socket server, the multi-hop remote access latency might be so slow
> that you need either NUMA placement or try to constrain your entire
> workload (memory and processes) into a single NUMA node, or 2-3 NUMA
> nodes that have the lowest latency between each other. You might find
> out that most of your current CPU "usage" is actually stalled CPU
> empty cycles, waiting for remote memory access...
>
> Note that at least on Intel/AMD platform you can use Intel's Memory
> Latency Checker (mlc) tool as I've done here in my hacking session:
>
> * https://www.youtube.com/watch?v=5A531KE8O9Q&t=3640s
> <https://www.youtube.com/watch?v=5A531KE8O9Q&t=3640s>
>
> --
> Tanel Poder
> https://learn.tanelpoder.com
>
>
> On Mon, Jun 20, 2022 at 5:10 AM Lothar Flatz <l.flatz_at_bluewin.ch> wrote:
>
> Thank you, Imar.
>
> Am 20.06.2022 um 10:24 schrieb Ilmar Kerm:
>> On OEL8/RHEL8 NUMA can be turned on:
>> Requirements for Installing Oracle Database/Client 19c on OL8 or
>> RHEL8 64-bit (x86-64) (Doc ID 2668780.1)
>>
>> On OEL7 recommendation was to turn it off:
>> Requirements for Installing Oracle Database 19c on OL7 or RHEL7
>> 64-bit (x86-64) (Doc ID 2551169.1)
>>
>> On Mon, Jun 20, 2022 at 10:11 AM Lothar Flatz
>> <l.flatz_at_bluewin.ch> wrote:
>>
>> Hi,
>>
>> I have a customer who runs a older Superdome Server with an 8
>> socket board (7 sockets used).
>> End of quarter processing is approaching and we would need
>> some performance boost.
>> In theory we should have Numa effects. The hidden parameters
>> for Numa ( "_enable_NUMA_support" = TRUE according to MOS Doc
>> ID 1956463.1) are not set.
>> I see a chance to get some quick improvement.
>> However, Numa is not my topic. I am a bit concerned by the
>> fact that the newest MOS entry I find dates back to db
>> version 12.1.
>> Well, these kind of servers are not widely used any more.
>> Can somebody shed some light on the issue? Is NUMA still an
>> issue in version 19c?
>> Can we expect some improvement stetting NUMA support in the db?
>>
>> Thanks
>>
>> Lothar
>>
>>
>>
>> --
>> Ilmar Kerm
>

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