[Info-vax] Intel junk...Kernel-memory-leaking Intel processor design flaw forces Linux, Windows redesign

[Alan Browne]

On 2018-01-05 10:51, Wolf K wrote:

> So, in order to reduce the performance hit, would it make sense to 
> redesign the CPU with a larger on-board cache to store both kernel and 
> user memory? Or, what am I missing in the protected memory concept?

Ignoring that the only fix will be in future (or currently in 
pre-production) CPU's, the fix could be done with the same sized caches 
but correctly implemented.  It could be the "correct fix" is itself less 
efficient overall than the goal (execution).  It could be that such a 
fix would reduce the amount of cache available to Kernel/User space and 
thus have an impact too.

New CPU's can have the luxury of more cache in any case and so can add 
even more to help with the issue.

Wow.  What a long winded way to say: "who knows?".

> 
> Anyhow, I think most users will see no performance hit. I mean, how many 
> people are rendering CGI on their laptops? Etc.
> 
> I'm more worried about server farms used by big data, banks, ISPs etc. 
> These already show performance hits tied to time-of-day, as user access 
> (ie demand) varies. Even a few % slowdown in overall throughput will be 
> noticeable at peak demand times.

That depends on the server farms.  Well designed they scale up cheaply 
(upscale effort) but expensively (hardware + energy).  There is cost.

AWS style platforms can upscale dynamically according to load (and the 
contract with the service client).  Of course the service client will be 
sad to see his costs with the platform go up and have to find a way to 
get more revenue.

All that said, the 5 - 30% load increase seems to be speculative / 
theoretical.  And maybe you're right that it will mostly affect people 
using their computers to the hilt a lot of the time and not most 
"casual" users.   Alas, I do render videos often but can't say my Mac 
(OS 10.13.2) has seen any impact (nor can I say it hasn't - nothing 
noticable IOW).

Maybe under 10.13.3 when Apple are rumoured to "complete" their defense 
against Meltdown and/or Spectre we'll perceive the hit.

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