Arch Linux

realmatrix

Member

Registered: 2019-01-10

Posts: 29

[SOLVED] No Hyper-Threading with Kernel 4.20 ?

Today I recognized that Hyper-Threading of my Core i5 (Quadcore) is disabled.
# lscpu:
Thread(s) pro Kern:            1
Kern(e) pro Socket:            4

Im not sure if it was made by firmware update of my Intel Desktop-Board, by intel-ucode (Microcode) or by Arch Kernel 4.20.
Encoding h.264 movie takes now 2x times !!! :-(
An Indicator was also conky, it shows never more than 50% cpu usage on every core.
Somebody an idea/same issue? What can I do to activate HT, is it a good idea in mind security?

Thanks a lot
realmatrix

Last edited by realmatrix (2019-01-16 19:28:03)

Potomac

Member

Registered: 2011-12-25

Posts: 528

Re: [SOLVED] No Hyper-Threading with Kernel 4.20 ?

maybe an explanation here :

https://www.phoronix.com/scan.php?page= … tibp&num=1
https://linux.slashdot.org/story/18/11/ … intel-cpus

An intentional kernel change in Linux kernel 4.20 for enhanced Spectre mitigation is unfortunately causing Intel Linux performance to be much slower than with 4.19. That change is 'STIBP' (Single Thread Indirect Branch Predictors), which allows for preventing cross-hyperthread control of decisions that are made by indirect branch predictors. It affects Intel systems that have up-to-date microcode and CPU Hyper Threading enabled. Phoronix gives the evidence.

Last edited by Potomac (2019-01-10 20:58:43)

loqs

Member

Registered: 2014-03-06

Posts: 17,323

Re: [SOLVED] No Hyper-Threading with Kernel 4.20 ?

The STIBP defaults were changed with https://github.com/torvalds/linux/commi … 1fcfde7621 before 4.20 was released.

realmatrix

Member

Registered: 2019-01-10

Posts: 29

Re: [SOLVED] No Hyper-Threading with Kernel 4.20 ?

Thanks, Problem is solved :-)

I used a terrible GUI for video encoding with totally wrong notifications and parameters. Now using 'handbrake' and everything works fine in well-known speed.

2ManyDogs

Forum Fellow

Registered: 2012-01-15

Posts: 4,645

Re: [SOLVED] No Hyper-Threading with Kernel 4.20 ?

Please remember to mark your thread [SOLVED] (edit the title of your first post).