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

[Dale]

J. Roeleveld wrote:
> On December 8, 2018 6:23:04 PM UTC, Dale <rdalek1967@×××××.com> wrote:
>
>     Alexander Puchmayr wrote:
>
>         Am Donnerstag, 6. Dezember 2018, 10:27:31 CET schrieb Dale:
>
>             Howdy, I mentioned in other threads that I'm doing some
>             upgrades to my system. My first question is about a CPU
>             upgrade. I currently have this for my CPU, from cpuinfo:
>             AMD Phenom(tm) II X4 955 Processor I've bought but not yet
>             installed a FX-8350 CPU. I have this in my make.conf file:
>             CFLAGS="-march=native -O2 -pipe"
>
>         Compiling the whole system with -march=native might lead to
>         troubles, especially when doing a CPU change. This option
>         means that gcc is determining the type of CPU automatically
>         and adjusts the instruction set used to exactly this CPU.
>         Although, in your case, it is highly likely that your new CPU
>         understands all commands from the old, but I wouldn't bet on
>         it. Its possible that your existing software encounters
>         problems like "illegal instruction" or the like. Very bad if
>         your compiler crashes after CPU replacement, then you cannot
>         emerge anything. I highly recommend using CFLAGS="-O2 -pipe"
>         and nothing more, the performance difference is, if measurable
>         at all, negligible.
>
>             USE_CPU="fpu vme de pse tsc msr pae mce cx8 apic sep mtrr
>             pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht
>             syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm 3dnowext
>             3dnow constant_tsc rep_good nopl nonstop_tsc extd_apicid
>             pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic
>             cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs
>             skinit wdt nodeid_msr hw_pstate npt lbrv svm_lock nrip_save"
>
>         As someone else in this thread already mentioned, USE_CPU is
>         not used. What you're looking for is CPU_FLAGS_X86=..., which
>         defines what cpu-specific options will be enabled for packages
>         supporting it and where it makes sense. See package
>         cpuid2cpuflags for details. Regards Alex
>
>
>     It seems the holiday shopping is slowing down delivery.  My fan was
>     supposed to be here today but didn't arrive.  Since I got time, I'll
>     change the CFLAGS for at least the @system stuff, that should get me
>     booted for sure.  While the native setting makes things easier for
>     normal use, I can see the point of not using it when changing CPUs. 
>     That is one reason for this thread.  The CPUs are different and may
>     require some changes during the swap. 
>
>     Is there a easy way to see what if any changes will be made?  I did a
>     emerge -UDNa @system but it's not showing any change.  Does it require a
>     emerge -e @system to force the change?  Or is it not changing anything?
>
>     Thanks much.  Better safe than sorry.  ;-)
>
>     Dale
>
>     :-)  :-) 
>
>
> A CFLAGS change requires a rebuild of all packages done with gcc. I am
> not aware of a simple way of only doing those, so a "emerge --empty
> @world" will be needed.
>
> --
> Joost
> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.


Based on the output, that's what I was thinking. Emerge picks up on
other USE changes but it seems it only grabs the CFLAGS during the
compile/configure phase for each package. Would this change the kernel
image as well or would it remain the same?  I may build a new kernel
just to be sure.

One good thing about this, I can compare the times with current CPU and
new CPU later and get a rough idea of speed increases.  ;-) 

Pardon me while I generate some heat.  o_O

Dale

:-)  :-)