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#1 2019-01-01 09:15:48

Batou
Member
Registered: 2017-01-03
Posts: 259

4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

Hi,

For few weeks now I've heard from people at work, who work in devops, that from their testing, 4.20 RCs have been noticeably slower than 4.19. They benchmark and test every kernel release before deploying and 4.20 is slower than 4.19 for their loads. I guess all the branch prediction exploit mitigations  have finally taken the toll.

I've just installed 4.20 on my desktop and on my laptop and I honestly can't 'feel' it on my desktop. I know it compiles codebases slower (compiling the kernel takes roughly 20 seconds longer than 4.19 for example) but I can't tell from just using the apps. On my laptop, however, with an older Intel i5, I think I can tell that it's not as snappy as before. When I have Firefox with dozens of tabs open, it's just not as snappy as before when I switch quickly between various tabs. It's not terrible but it's definitely not as fast as before.

So, has anyone else noticed any slowdowns?
Will you disable all or some of the mitigations?

I'm curious what others think... I'm leaning towards disabling some of the mitigations but I'm not certain yet. Any thoughts?


Please vote for all the AUR packages you're using. You can mass-vote for all of them by doing: "pacman -Qqm | xargs aurvote -v" (make sure to run "aurvote --configure"  first)

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#2 2019-01-01 14:08:24

jsoy9pQbYVNu5nfU
Member
Registered: 2013-04-19
Posts: 108

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

Thinkpad laptop with 5 y/o i5-4210U CPU here. Snappiness was indeed affected, even for everyday applications like Firefox, TeXLive compilations. Unacceptable for my main and only PC.

I'm disabling all mitigations using

pti=off spectre_v2=off l1tf=off nospec_store_bypass_disable no_stf_barrier

I'm also keeping intel-ucode @ 20171117-1 and the laptop UEFI firmware old enough so it doesn't include recent microcode updates.

With this setup, there are no noticable differences between 4.14, 4.19, 4.20. I don't explicitly recommend this but as long as the choice is there I'll take it. The risks are well documented.

Last edited by jsoy9pQbYVNu5nfU (2019-01-01 14:08:59)

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#3 2019-01-01 14:40:03

ugjka
Member
From: Latvia
Registered: 2014-04-01
Posts: 1,794
Website

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

i started notice it with hd videos stuttering in firefox


https://ugjka.net
paru > yay | webcord > discord
pacman -S spotify-launcher
mount /dev/disk/by-...

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#4 2019-01-01 14:57:01

Trilby
Inspector Parrot
Registered: 2011-11-29
Posts: 29,442
Website

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

Ah ... so some engineers took some really stupid and short-sighted short cuts to make their processor "faster" which - no surprise - came at a substantial security cost which we are only now learning how to deal with.  And several of you now would prefer to tear down all the mitigations and go forward with the snappy but totally foolishly designed shortcuts?

Good luck with that.

Are you also suspicious that your car could go faster if you get rid of the brakes and and all steering systems?   And just in case, ditch the air bags and the seatbelts - it may not be much, but they're just extra weight.

Last edited by Trilby (2019-01-01 19:22:09)


"UNIX is simple and coherent..." - Dennis Ritchie, "GNU's Not UNIX" -  Richard Stallman

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#5 2019-01-02 02:00:44

Batou
Member
Registered: 2017-01-03
Posts: 259

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

Trilby wrote:

Ah ... so some engineers took some really stupid and short-sighted short cuts to make their processor "faster" which - no surprise - came at a substantial security cost which we are only now learning how to deal with.  And several of you now would prefer to tear down all the mitigations and go forward with the snappy but totally foolishly designed shortcuts?

Good luck with that.

Are you also suspicious that your car could go faster if you get rid of the brakes and and all steering systems?   And just in case, ditch the air bags and the seatbelts - it may not be much, but they're just extra weight.

It all depends on what your security threat model is. The riskiest application that I run is the web browser. Everything else doesn't even come close to it. I run it sandboxed plus it has its own per-tab sandboxing as well. And given how they removed the high-precision timer from the JS engine, I don't see how Meltdown/Spectre can impact me. The threat is really minimal to my use case.

However, if you're a service provider who runs lots of virtualization stuff, well, then you're screwed and you need to enable all that stuff or pay the 20-25% performance penalty.


Please vote for all the AUR packages you're using. You can mass-vote for all of them by doing: "pacman -Qqm | xargs aurvote -v" (make sure to run "aurvote --configure"  first)

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#6 2019-01-02 02:17:04

Alad
Wiki Admin/IRC Op
From: Bagelstan
Registered: 2014-05-04
Posts: 2,407
Website

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

I added the following option to the kernel command line:

alad-likes=hannah-montana

My system now feels 37.1% snappier.


Mods are just community members who have the occasionally necessary option to move threads around and edit posts. -- Trilby

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#7 2019-01-02 02:21:32

Steef435
Member
Registered: 2013-08-29
Posts: 577
Website

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

To be fair, the current situation seems more like getting a car without brakes and then after a few years they find this has its security implications, and the solution is to softwarematically lock the max speed to 30 km/h. (instead of adding brakes, because the broken architecture can't be fixed without hardware changes)

So far I haven't noticed a thing though, and I like my brakes. So I'll leave them on until I can replace this system with non broken hardware.

EDIT: reworded to remove unintended nuance

Last edited by Steef435 (2019-01-02 02:22:39)

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#8 2019-01-26 04:14:10

mountaineerbr
Banned
Registered: 2018-12-08
Posts: 48

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

ugjka wrote:

i started notice it with hd videos stuttering in firefox

Google has been know slow down youtube on other browser than not his own.
Check this out:

https://www.techtimes.com/articles/2326 … irefox.htm

You can install an extension which will ask youtube for the old API (which would only be available for Internet Explorer 11 users, otherwise)

I was having this youtube slowdown and that worked for me.

I am also disabling all mitigations as  2ion suggested, and will check for performance improvement...

Thanks

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#9 2019-01-26 07:38:49

ugjka
Member
From: Latvia
Registered: 2014-04-01
Posts: 1,794
Website

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

mountaineerbr wrote:
ugjka wrote:

i started notice it with hd videos stuttering in firefox

Google has been know slow down youtube on other browser than not his own.
Check this out:

https://www.techtimes.com/articles/2326 … irefox.htm

You can install an extension which will ask youtube for the old API (which would only be available for Internet Explorer 11 users, otherwise)

I was having this youtube slowdown and that worked for me.

I am also disabling all mitigations as  2ion suggested, and will check for performance improvement...

Thanks

It was not just youtube, also reddit gifs/videos and even soundcloud audio player stuttered


https://ugjka.net
paru > yay | webcord > discord
pacman -S spotify-launcher
mount /dev/disk/by-...

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#10 2019-01-26 15:18:29

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 19,739

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

What would one expect of a system with a release number of 4.20 ?
[I don't actually know if that makes sense outside of the USA.  I don't partake.]

Last edited by ewaller (2019-01-26 15:18:59)


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

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#11 2019-01-26 15:43:55

qinohe
Member
From: Netherlands
Registered: 2012-06-20
Posts: 1,494

Re: 4.20 is out. Is it slower for you (on Intel)? Disable mitigations?

ewaller wrote:

What would one expect of a system with a release number of 4.20 ?

Smoke, lots smoke

[I don't actually know if that makes sense outside of the USA.  I don't partake.]

Hehe maybe not but you are the first that lays the link... tongue

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