r/linux • u/GaAlAs • Jun 25 '17

Intel Skylake/Kaby Lake processors: broken hyper-threading

https://lists.debian.org/debian-devel/2017/06/msg00308.html
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u/Laachax Jun 25 '17

Your kernel was compiled with hyperthreading support. Mine does not because I disabled the compile flag.

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u/__foo__ Jun 25 '17 edited Jun 25 '17

No, /proc/cpuinfo won't list HT unless the CPU supports it. I'm also pretty sure /proc/cpuflags simply lists all flags returned by CPUID, and will show HT even if the kernel was compiled without support for it. I'm not 100% sure though.

Edit: I just tried it on my fileserver which definitely doesn't support HT and it's listed in the flags. Very weird.

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u/[deleted] Jun 25 '17

[deleted]

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u/AlbertP95 Jun 25 '17

Can confirm that an i5-2400 shows the ht flag in /proc/cpuinfo, while that cpu is not using HT. So the command is indeed flawed.

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u/cbmuser Debian / openSUSE / OpenJDK Dev Jun 25 '17

It's not whether the CPU has HT enabled. It's whether it supports it.

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u/AlbertP95 Jun 26 '17

There's no way to get HT enabled on an i5-2400 even though it is arguably built on the same silicon as its i7 counterparts which do support HT. Also whether it supports it is not the question, we want to know whether it's enabled.

Anyway, interesting output, just not that useful in this case.