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

On 03/27 11:51, Mark Knecht wrote:
> 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

Hi Mark,

thank you for your explanations! :)

/proc/cpu doesn't exist on my system....may be you are referring to
/proc/cpuinfo?

The problem was caused by a kernel misconfiguration by me.

In the kernel setup there is a setting "Number of cores" which
I had set to six ... since my CPU has 6 physical core.

Setting this to twelve (and blurring the syntactically border between
threads and cores thereby...) gives me twelves cores in top, htop
and such and (as an example) compiling the kernel is faster -
so it is not a display gimmick only.

I think "Number of cores" is a misnomer...or am I wrong?

Cheers!
Meino