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Author: Steve Litt
To: dng
Subject: Re: [DNG] Ascii to Beowulf upgrade - 32% slowdown !
On Sun, 14 Jun 2020 08:46:48 +0200
Riccardo Mottola via Dng <dng@???> wrote:

> Hi,
> On 6/12/20 9:21 PM, Steve Litt wrote:
> >> Maybe try ;https://make-linux-fast-again.com/ kerneloptions to
> >> disable all spectre and meltdown stuff
> > I hope you mean the preceding as a diagnostic test and not as a
> > solution.
> first, diagnostic on what is slowing down and stealing performance in
> such a significant way.
> second, it could be also acceptable as a solution: If a system like
> laptop is not running multi-user, no virtual machines and you
> consider the software running trusted, where are the risks? I think
> only in the browser which runs "unknown" and "untrusted" stuff: The
> only attack surface would be JavaScript (or Java, Flash or similar).
> If, from what I read, the browser removed high resolution timers,
> timing attacks needed to exploit these bugs are unlikely.
> Am I simplifying too much and overseeing some holes?

In my opinion, yes. What if a browser didn't remove the high resolution
timers? What if other software, currently considered "trusted", acts as
a vehicle for the exploit? What if the badguys know more about exploits
than you?

Making sure you use the right browsers and only trusted apps in the
face of a virus like this strikes me like wearing a mask and using
plenty of hand cleaner and then hanging around in a meat packing plant.
Yeah, you've taken all the precautions you know to take, but you've
placed yourself right in the flight path of the virus.

There's something else too. The OP measured 32% slowdown on one
activity. We don't know whether that kind of performance is common to
most activities. Removing protection against known exploits to cure a
problem with an unknown cause and an unknown range is the ultimate in
proceeding on an untested assumption.

Until the root cause is known, no solution should be applied, and
diagnostic tests should be performed in a safe manner.


Steve Litt 
May 2020 featured book: Troubleshooting Techniques
     of the Successful Technologist