Re: Major CPU bugs - Was: Christmas present for self.

Rob <rob@xxxxxxxxxxxxxxx> · Thu, 4 Jan 2018 21:09:25 +0000



    On 04/01/18 19:56, Paul Davis wrote:

    
          On Thu, Jan 4, 2018 at 2:43 PM, Robin
            Gareus <robin@xxxxxxxxxx>
            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 tha 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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