Re: [gentoo-user] RYZEN 5: Hyperthreading or no hyperthreading...

[Mark Knecht]

On Fri, Mar 27, 2020 at 11:11 AM <tuxic@××××××.de> wrote:
>
> On 03/27 06:04, Andrea Conti wrote:
> > Hello,
> >
> > > Thread(s) per core:              1 <<<<<
> > > Does my CPU hyperthread?
> >
> > Definitely not.
> >
> > Your kernel config is fine, chances are hyperthreading (aka "SMT mode")
is
> > disabled in your BIOS settings.
> >
> > andrea
> >
>
> Hi Andrea,
>
> I checked that: The BIOS setting was set to use hyperthreading.
>
> But "Number of cores" was set to six. I changed that to 12 and
> Voila! I got two threads per core.
>
> I think "Number of cores" is a little misleading, since there
> are six physical cores (not threads) with a RYZEN 5.
>
> I feeling not that comfortable with this solution.
>
> Is there any way to check for the validity of this setting
> beside a tool, which prints a "2" after the word "threads" ;) ?
>
> Cheers!
> Meino
>
>

cat /proc/cpu should give info for each thread. I've been running an i7 980
Extreme processor @3.33GHz here at home for about 12 years or so. It's 6
cores but shows 12 processors on both Gentoo and now Kubuntu.

I generally run top and then hit '1' and 'z'. You can watch what percentage
each core/thread is using.

Time a BIG compile job twice, once with each kernel. If it's working you'll
measure a significant difference in time. Note that it won't be 2x as
you'll also be limited by disk read/write throughput, but you'll know it's
basically working.

On Gentoo make sure you're compile settings in (I think make.conf - I no
longer run Gentoo much) are set to take advantage of all your cores and not
limited to something smaller. Also watch overheating when using more
cores/threads. On older PCs like mine when you possibly have dust in CPU
coolers might not be as efficient as when they are new.

HTH,
Mark