On Saturday 16 August 2014 23:51:46, Philip Guenther wrote: > > Yes, code patching may be useful. I haven't noticed it used in > > openbsd before, but I will take a look at sparc64. > > Code patching is used currently on i386 and amd64 for the SMAP > support. Grep for _copyin_stac, for example.
Thanks. I have already noticed that. Recently, I have however worked on improving pmap instead. Basically instead of making IPIs faster on KVM, do much fewer IPIs. I will write about that in a new thread, though. For paravirtualization, it seems it is not always obvious which features to use. If the host machine is very new and has certain VMX hardware features (e.g. "Virtual interrupt delivery" and "APIC register emulation"), some of paravirtualizaion techniques that have significant positive effect on older hardware may instead cause a slowdown. I am not sure that KVM always provides enough information to make the best choice automatically. I fear this will require quite a few knobs for tuning.
