Hi all,
Recently I met an odd performance problem: when I turn on APIC
Virtualization feature (apicv=1), the network performance of a windows
guest become worse.
My test case like this: host only have one windows 2008 R2 HVM
guest running,and this guest has a SR-IOV VF network passthrough to it.
Guest using this network access a NAS device. No fontend or backend of
network and storage, all data transfered through network.
The xentrace data shows: the mainly difference between apicv and
non-apicv, is the way guest write apic registers, and
EXIT_REASON_MSR_WRITE vmexit cost much more time than
EXIT_REASON_APIC_WRITE, but when using WRMSR, the PAUSE vmexit is much
less than using APIC-v.
This is the odd part,any ideas?
APIC-v OFF:
4099582 VMEXIT 3467051359128 TSC HLT
10135140 VMEXIT 42484175528 TSC WRMSR
1651714 VMEXIT 9785961276 TSC I/O instruction
532702 VMEXIT 3887971388 TSC External interrupt
290546 VMEXIT 2262312440 TSC PAUSE
588077 VMEXIT 914905312 TSC Control-register accesses
383617 VMEXIT 453329940 TSC Exception or non-maskable
interrupt (NMI)
132717 VMEXIT 232289792 TSC Interrupt window
25534 VMEXIT 198718764 TSC EPT violation
53969 VMEXIT 62886752 TSC TPR below threshold
7996 VMEXIT 34735376 TSC RDMSR
1615 VMEXIT 16042768 TSC VMCALL
147 VMEXIT 272320 TSC CPUID
7 VMEXIT 6484 TSC WBINVD
2 VMEXIT 6308 TSC MOV DR
APIC-v ON:
3717629 VMEXIT 3459905385332 TSC HLT
2282403 VMEXIT 23099880196 TSC APIC write
3900448 VMEXIT 13073253548 TSC PAUSE
1643729 VMEXIT 11719626776 TSC I/O instruction
2194667 VMEXIT 5321640708 TSC WRMSR
214425 VMEXIT 2198994944 TSC External interrupt
566795 VMEXIT 1940710108 TSC Control-register accesses
342688 VMEXIT 659665532 TSC Exception or non-maskable
interrupt (NMI)
190623 VMEXIT 644411612 TSC VMCALL
188657 VMEXIT 295956932 TSC Virtualized EOI
24350 VMEXIT 194817152 TSC EPT violation
4393 VMEXIT 23282044 TSC RDMSR
179 VMEXIT 1688676 TSC CPUID
7 VMEXIT 6884 TSC WBINVD
1 VMEXIT 4200 TSC MOV DR
In commit 7f2e992b824ec62a2818e64390ac2ccfbd74e6b7
"VMX/Viridian: suppress MSR-based APIC suggestion when having APIC-V",
msr based apic is disabled when apic-v is on, I wonder can they co-exist
in some way? seems for windows guest msr-based apic has better performance.
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
