[gentoo-user] Re: CPU upgrade and LVM questions.

[Nikos Chantziaras <realnc@gmail.com>]

On 06/12/2018 23:45, Dale wrote:
>>
>> You won't get anything close to double the speed. The extra cores will
>> mostly go unused, unless you use applications that make use of them.
>>
>> You will still get a speed up due to the newer CPU architecture and
>> the higher frequency.
> 
> What I was thinking about is something like when compiling and all the
> cores are used.  In other words, CPU is at max load.  Right now, I have
> only 4 cores.  New CPU doubles that and each core is faster as well.  As
> a example, Firefox takes about a hour to compile.  I was hopeful that
> would drop to 30 or 35 minutes or so.

Oh that. Yeah, there will be a 2x speedup when emerging packages 
(MAKEOPTS="-j8"). I was referring to application performance when using 
the machine. I don't consider package installation as "using the 
machine" :-)


>> The two speeds specify the lower and upper speeds, depending on how
>> many CPU cores are currently being under load, and also how much load
>> there is. You don't have to worry about it though. It's all automatic.
>> [...]
> 
> That's good to know.  That I was wondering about and couldn't find a
> clear answer on.  I didn't know if I needed to install something to
> manage that or what.

The kernel takes care of that. You should be able to observe the CPU's 
frequency and temperature in KSysGuard. Here's how it looks here:

   https://i.imgur.com/Xogy3h0.png

In that screenshot, the CPU has all 4 cores clocked down to 1.6GHz 
because they're all mostly idle. Once there's high CPU load, it will 
crank up the clocks towards 4GHz.

You need to add these sensors manually to KSysGuard though. But if you 
do, it's a good way to verify things are working as intended.