Re: SMT8

[Roberto José Etcheverry Romero <yggdrasil.raiker@xxxxxxxxx>]

Rob,
I've just asked a POWER8 hardware architect and he says that at least aix
has smt4 as default to avoid software scaling problems but it's better to
have the threads running rather than sleeping.
So enabling smt8 should either benefit or do nothing only in rare cases
would thread contention lower the system performance. Another thing is that
if you're running 80% or more cpu utilization you will see no benefit or
actually lower performance due to utilization getting too high.
I think that's all.
On how to enable smt8 I forgot to ask him...

Best Regards

Roberto
On Sep 2, 2015 8:51 AM, <rob@xxxxxxxxx> wrote:

> Have y'all played with SMT8 yet?  I am running all Power 8's; two 814's
> and one 824.  They are running multiple LPARs:  IBM i 7.1-15142-TR10, IBM
> i 7.2-15135-TR2, VIOS 2.2.3.4, AIX 7.1.0.0, FW810.21 (108)
>
> I've checked a few websites and I'm having a tough time just trying to
> figure out how to turn it on.
>
> I'm also trying to figure out if different lpars may benefit more than
> others, or may it actually hurt performance on any.
>
> First, I think we can safely assume that none of these lpars are a single
> user machine which only runs one batch program at a time using traditional
> I/O for ERP processing.
> Many support Domino and/or WAS and many of these lpars are dedicated to
> just such a workload.
>
> Links I've read:
> http://www.itjungle.com/tfh/tfh060214-story01.html
>
> http://www-01.ibm.com/support/knowledgecenter/ssw_ibm_i_72/rzahx/rzahxmultithread.htm?lang=en
>
> http://www-01.ibm.com/support/knowledgecenter/ssw_ibm_i_72/rzakz/rzakzqprcmlttsk.htm?lang=en
>
>
> Rob Berendt
> --
> IBM Certified System Administrator - IBM i 6.1
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