[LAU] Major CPU bugs - Was: Christmas present for self.

[Rob]

On 04/01/18 19:56, Paul Davis wrote:
>
> On Thu, Jan 4, 2018 at 2:43 PM, Robin Gareus <robin at gareus.org 
> <mailto:robin at gareus.org>> wrote:
>
>
>     Depends on your DAW. In Ardour's case there is no context-switch. All
>     tracks, Busses and FX run in the same process. So there won't be any
>     direct effect.
>
>     Low-latency I/O however (soundcard) will see additional overhead, as
>     will JACK with multiple clients (one context switch per client).
>
>
> ​is this correct? my impression is that KPTI makes user->kernel and 
> kernel->user switches more expensive th​a they used to be, but does 
> not change the cost of a context switch that stays in the same ring mode.
> ​
> so, basically, system calls cost more; context switches stay at about 
> the same cost.

https://lwn.net/Articles/741878/ - top-most page table is duplicated and 
stripped of kernel pages; duplicate is active when running userspace.

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