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
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