4 ms·
Yup, I think so. In that case (PCID hardware on a PCID-enabled kernel), the performance effect should be more limited to the syscall itself. That said, why is
by BeeOnRope 9y ago
Yup, I think so.
In that case (PCID hardware on a PCID-enabled kernel), the performance effect should be more limited to the syscall itself. That said, why is the hit still so big with PCID? Surely just the CR3-swap by itself shouldn't be so slow?
- bonzini 9y agoMOV-to-CR3 is pretty slow, yes. In the ballpark of a hundred clock cycles, and you have to do 2 of them. The cost of a system call was about 1000 cycles, maybe less on newer processors---both OSes and processors optimize the hell out of SYSCALL/SYSRET.