Re: performance with guests running 2.4 kernels (specifically RHEL3)

["David S. Ahern" <daahern@cisco.com>]

Avi Kivity wrote:
> 
> Ah!  The flood detector is not seeing the access through the
> kmap_atomic() pte, because that access has gone through the emulator. 
> last_updated_pte_accessed(vcpu) will never return true.
> 
> Can you verify that last_updated_pte_accessed(vcpu) indeed always
> returns false?
> 

It returns both true and false. I added a tracer to kvm_mmu_pte_write() to dump
the rc of last_updated_pte_accessed(vcpu). ie.,
	pte_access = last_updated_pte_accessed(vcpu);
        KVMTRACE_1D(PTE_ACCESS, vcpu, (u32) pte_access, handler);

A sample:

(+    4488)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c016104a ]
(+       0)  PAGE_FAULT   [ errorcode = 0x0000000b, virt = 0x00000000 fffb63b0 ]
(+    2480)  PAGE_FAULT1  [ write_count = 0 ]
(+     424)  PAGE_FAULT2  [ level = 2 metaphysical = 0 access 0x00000007 ]
(+   51672)  PAGE_FAULT3
(+     472)  PAGE_FAULT4
(+     704)  PAGE_FAULT5  [ shadow_ent = 0x80000001 2dfb5043 ]
(+    1496)  VMENTRY
(+    4568)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c01610e7 ]
(+       0)  PAGE_FAULT   [ errorcode = 0x00000003, virt = 0x00000000 c0009db4 ]
(+    2352)  PAGE_FAULT1  [ write_count = 0 ]
(+     728)  PAGE_FAULT5  [ shadow_ent = 0x00000001 91409041 ]
(+       0)  PTE_WRITE    [ gpa = 0x00000000 00009db4 gpte = 0x00000000 41fb5363 ]
(+       0)  PTE_ACCESS   [ pte_access = 1 ]
(+    6864)  VMENTRY
(+    3896)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c01610ee ]
(+       0)  PAGE_FAULT   [ errorcode = 0x00000003, virt = 0x00000000 c0009db0 ]
(+    2376)  PAGE_FAULT1  [ write_count = 1 ]
(+     720)  PAGE_FAULT5  [ shadow_ent = 0x00000001 91409041 ]
(+       0)  PTE_WRITE    [ gpa = 0x00000000 00009db0 gpte = 0x00000000 00000000 ]
(+       0)  PTE_ACCESS   [ pte_access = 0 ]
(+   12344)  VMENTRY
(+    4688)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c016127c ]
(+       0)  PAGE_FAULT   [ errorcode = 0x00000003, virt = 0x00000000 c0009db4 ]
(+    2416)  PAGE_FAULT1  [ write_count = 2 ]
(+     792)  PAGE_FAULT5  [ shadow_ent = 0x00000001 91409043 ]
(+    1128)  VMENTRY
(+    4512)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c016104a ]
(+       0)  PAGE_FAULT   [ errorcode = 0x0000000b, virt = 0x00000000 fffb63b0 ]
(+    2448)  PAGE_FAULT1  [ write_count = 0 ]
(+     448)  PAGE_FAULT2  [ level = 2 metaphysical = 0 access 0x00000007 ]
(+   51520)  PAGE_FAULT3
(+     432)  PAGE_FAULT4
(+     696)  PAGE_FAULT5  [ shadow_ent = 0x80000001 2df5a043 ]
(+    1480)  VMENTRY


david

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