On 9/18/18 8:28 AM, Jan Beulich wrote: > Having noticed that VMLOAD alone is about as fast as a single of the > involved WRMSRs, I thought it might be a reasonable idea to also use it > for PV. Measurements, however, have shown that an actual improvement can > be achieved only with an early prefetch of the VMCB (thanks to Andrew > for suggesting to try this), which I have to admit I can't really > explain. This way on my Fam15 box context switch takes over 100 clocks > less on average (the measured values are heavily varying in all cases, > though). > > This is intentionally not using a new hvm_funcs hook: For one, this is > all about PV, and something similar can hardly be done for VMX. > Furthermore the indirect to direct call patching that is meant to be > applied to most hvm_funcs hooks would be ugly to make work with > functions having more than 6 parameters. > > Signed-off-by: Jan Beulich <jbeul...@suse.com> > Acked-by: Brian Woods <brian.wo...@amd.com> > --- > v3: Add/extend comments. > v2: Re-base. > --- > Besides the mentioned oddity with measured performance, I've also > noticed a significant difference (of at least 150 clocks) between > measuring immediately around the calls to svm_load_segs() and measuring > immediately inside the function.
Reviewed-by: Boris Ostrovsky <boris.ostrov...@oracle.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
