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

Robin Gareus robin at gareus.org
Thu Jan 4 21:17:03 UTC 2018


On 01/04/2018 10:09 PM, Rob wrote:
> 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.
> 

Thanks for the heads up. I stand corrected.



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