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Disable HyperThreading on Skylake and Kaby Lake?

asked 2017-06-27 08:51:06 -0500

VaporTrail gravatar image

updated 2018-11-04 04:13:52 -0500

hhlp gravatar image

As I understand this issue, it effects any OS, not just Debian. If so, is there a software patch for Fedora as Dell hasn't yet released any firmware updates for my systems effected by this.

http://news.softpedia.com/news/debian...

I've turned off HyperThreading but I honestly don't know I should turn HT back on and not worry or play it safe and leave it off? For that matter, I don't know if HT is of any real benefit to me?

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answered 2017-06-27 10:40:28 -0500

muep gravatar image

At the moment of writing, the microcode update for Kaby Lake does not seem to be available for GNU/Linux distributions which I'd guess is why the Debian message recommends disabling hyper-threading for Kaby lake users.

For Skylake, changelog of microcode_ctl on F25 looks like it just might have the fixes mentioned in the message:

* Tue May 23 2017 Anton Arapov <aarapov@redhat.com> 2:2.1-15
- Update to upstream 2.1-12. 20170511

I do not know how to verify this because following the instructions in the message would require me to have a Skylake CPU.

Especially if you have a higher-end CPU with four full cores and hyper-threading, you will likely not notice much difference in performance of day-to-day use regardless of disabling hyper-threading. It may help if you run many CPU intensive programs at the same time. So if you want to play it really safe, you might disable HT and see if you notice any difference. On the other hand, there does not seem to be an internet-wide panic about this despite it affecting some really popular CPUs, so in my view it would be quite reasonable to keep HT enabled and following the news a bit to see if the situation changes. I have been following the discussion on lwn.net.

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answered 2017-08-14 00:15:53 -0500

fedoramonsecond gravatar image

I just found out about this bug. Is disabling HT still required for Skylake CPU systems or an updated fedora 26 installation shouldn't have any problem because of the updated microcode? Many thanks!

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answered 2017-06-27 11:53:52 -0500

VaporTrail gravatar image

On the other hand, there does not seem to be an internet-wide panic about this despite it affecting some really popular CPUs

Good point. Thanks for the link, btw

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Asked: 2017-06-27 08:51:06 -0500

Seen: 430 times

Last updated: Aug 14 '17