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

[james <garftd@verizon.net>]

On 3/28/20 9:24 AM, tuxic@posteo.de wrote:
> On 03/28 05:59, Mark Knecht wrote:
>> On Fri, Mar 27, 2020 at 10:58 PM <tuxic@posteo.de> wrote:
>>>
>>> On 03/27 11:51, Mark Knecht wrote:
>>>> On Fri, Mar 27, 2020 at 11:11 AM <tuxic@posteo.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
>>>
>>
>> Meino,
>>     Yes, /proc/cpuinfo. Sorry.
>>
>>     Well yes, I guess the 'Number of cores' is a misnomer if you're trying
>> to equate the language in the kernel against Intel/AMD marketing data for
>> physical cores. 6 physical cores with or without hyperthreading is still 6
>> physical cores. However 6 physical cores (my processor) _WITH_
>> hyperthreading enabled is 12 _LOGICAL_ cores which is more what I think the
>> kernel verbiage is about. Semantics I suppose.
>>
>>     I'm glad you found it wasn't a gimmicky number. It really does work,
>> within the limits of the hardware being able to figure out what one thread
>> should be fetching or writing while the other thread is computing. It's not
>> a perfect 2:1 like 12 physical cores might be, but it's a lot less silicon
>> and therefore a lot less expensive.
>>
>> Cheers,
>> Mark
> 
> Hi Mark,
> 
> In the meanwhile I found "glance" and installed it, which is the
> bazooka-out-of-the-box-no-configuration terminal-brethren of "conky"
> :)
> 
> Enough plugins enabled (which come with it preinstalled), you can
> watch in realtime, what each core/thread is doing right now...nearly. Big
> Brother for the sustem with no bad intention in mind. I am only
> curious :)
> 
> And you get your sensors diplayed, the workload of your GPU (nvidia in
> my case), all processes and lot lot more.
> 
> The faster the CPU gets (my previous PC was 12 years old...), the
> more the peripheral devices are becoming show stoppers ("stoppers"
> in the barest truth of its meaning).
> 
> Unfortunatelu the SSD I ordered is in status "ready for delivery"
> since 23.03.2020....corona....you know...
> 
> And with 12 cores enabled on a recent CPU and running for example a
> bigger update via emerge (enabled for 12 threads of course)
> ...all the cores are simply waiting a lot
> faster......for the harddisc :)
> 
> Thanks for your help -- stay healthy!
> 
> Cheers!
> Meino

Meino,

You might like the organization and details of

"sys-process/htop"

to look at cores and processes.


hth,
James