2017-11-29 01:31-0800, Wanpeng Li: > From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > > MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT, so it is saved/restored > each time during world switch. Jim from Google pointed out that > when running schbench in L2, vmx_vcpu_run will occupy 4% cpu time, > and the 25% of vmx_vcpu_run cpu time is occupied by get_debugctlmsr(). > This patch caches the host IA32_DEBUGCTL MSR and saves/restores > the host IA32_DEBUGCTL msr when guest/host switches to avoid to > save/restore each time during world switch. > > Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Cc: Jim Mattson <jmattson@xxxxxxxxxx> > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> > --- Queued, thanks. And there is another optimization loosely connected to the "[PATCH v3 00/16] Move vcpu_load and vcpu_put calls to arch code" series: We only need to read the value for the KVM_RUN ioctl.
