Why does Red Hat and Fedora software not distinguish between AMD and Intel kernels?

[Reindl Harald]

Am 07.02.2014 15:21, schrieb James Harrison:
> I remember the times when Redhat software releases (6.2, 7.3, 8, 9) had a specific kernel for AMD and Intel CPUs.

times are changing

> Now forward on to present day and Red Hat software has one kernel build for AMD and Intel CPUs. 
> When was the decision to switch to an all in one encompassing kernel and is there a performance hit. 
> What allows us to have one kernel build for two different CPUs? 
> 
> The reason I ask these questions is that Ubuntu is still distinguishing between AMD and Intel CPUs. Why, 
> and what is the difference between what they do and what Red Hat do to their Kernel compiles.
> 
> Personally, I think that what Red Hat are doing makes maintaining kernels easier. There is a layer of 
> abstraction that hides what the underlying technology is

for the relevant things the kernel has ASM code
on a modern SandyBridge as example it uses AVX if available

for most code there is no difference which can be easily tested by
mtune=corei7-avx and generic while often result in a identical binary
and if there is a difference you need to draw the line between
theory and real runtime differences compared to maintainance burden

if you have a IvyVdrige CPU which supports "rdrand" instructions
they are used and additionally thrown in the random pool. if not
the kernel does not care
_________________________________________

take a look at "lsmod", these are all intel-specific modules
if the CPU supports AES-NI for hw-accelerated crypto, a own
kernel optimized for Intel would not do anything different
in that context

crct10dif_pclmul       14289  0
crc32_pclmul           13113  0
crc32c_intel           22079  0
ghash_clmulni_intel    13259  0