On Wed, 21 Apr 2010, Avi Kivity wrote:
On 04/21/2010 09:50 PM, Gerhard Wiesinger wrote:
I don't think changing VGA window is a problem because there are
500.000-1Mio changes/s possible.
1MB/s, 500k-1M changes/s.... Coincidence? Is it taking a page fault
or trap on every write?
To clarify:
Memory Performance writing to segmen A000 is about 1MB/st.
That indicates a fault every write (assuming 8-16 bit writes). If you're
using 256 color vga and not switching banks, this indicates a bug.
Yes, 256 color VGA and no bank switches involved.
Calling INT 10 set/get window function with different windows (e.g.
toggling between window page 0 and 1) is about 500.000 to 1Mio function
calls per second.
That's suprisingly fast. I'd expect 100-200k/sec.
Sorry, I mixed up the numbers:
1.) QEMU-KVM: ~111k
2.) QEMU only: 500k-1Mio
Please run kvm_stat and report output for both tests to confirm.
See below. 2nd column is per second statistic when running the test.
To get real good VGA performance both parameters should be:
About >50MB/s for writes to segment A000
~500.000 bank switches per second.
First should be doable easily, second is borderline.
I think this is very easy to distingish:
1.) VGA Segment A000 is legacy and should be handled through QEMU and not
through KVM (because it is much more faster). Also 16 color modes should be
fast enough there.
2.) All other flat PCI memory accesses should be handled through KVM (there
is a specialized driver loaded for that PCI device in the non legacy OS).
Is that easily possible?
No. Code can run in either qemu or kvm, not both. You can switch between
them based on access statistics (early versions of qemu-kvm did that, without
the statistics part), but this isn't trivial.
Hmmm. Ok, 2 different opinions about the memory write performance:
Easily or not possible?
Thnx for you help so far.
Ciao,
Gerhard
--
http://www.wiesinger.com/
-------------
kvm_stat
Please mount debugfs ('mount -t debugfs debugfs /sys/kernel/debug')
and ensure the kvm modules are loaded
lsmod|grep -i kvm
kvm_amd 38276 0
kvm 162288 1 kvm_amd
mount|grep -i debug
=>
mount -t debugfs debugfs /sys/kernel/debug
int10perf: INT10h Performance tests:
kvm statistics
efer_reload 0 0
exits 37648629 456206
fpu_reload 8512535 455983
halt_exits 2084 0
halt_wakeup 2047 0
host_state_reload 8513213 456011
hypercalls 0 0
insn_emulation 29182065 0
insn_emulation_fail 0 0
invlpg 0 0
io_exits 8386082 455975
irq_exits 51713 214
irq_injections 21797 36
irq_window 0 0
largepages 0 0
mmio_exits 242781 0
mmu_cache_miss 150 0
mmu_flooded 0 0
mmu_pde_zapped 0 0
mmu_pte_updated 0 0
mmu_pte_write 8192 0
mmu_recycled 0 0
mmu_shadow_zapped 151 0
mmu_unsync 0 0
mmu_unsync_global 0 0
nmi_injections 0 0
nmi_window 0 0
pf_fixed 16935 0
pf_guest 0 0
remote_tlb_flush 2 0
request_irq 0 0
request_nmi 0 0
signal_exits 1 0
tlb_flush 2251 0
Running VGA memory tests in same VGA page in Video Mode VESA 101h:
kvm statistics
efer_reload 0 0
exits 18470836 554582
fpu_reload 2147833 3469
halt_exits 2083 0
halt_wakeup 2047 0
host_state_reload 2148186 3470
hypercalls 0 0
insn_emulation 7688203 554244
insn_emulation_fail 0 0
invlpg 0 0
io_exits 10701583 18
irq_exits 50781 321
irq_injections 25251 18
irq_window 0 0
largepages 0 0
mmio_exits 162847 3241
mmu_cache_miss 154 0
mmu_flooded 0 0
mmu_pde_zapped 0 0
mmu_pte_updated 0 0
mmu_pte_write 8192 0
mmu_recycled 0 0
mmu_shadow_zapped 155 0
mmu_unsync 0 0
mmu_unsync_global 0 0
nmi_injections 0 0
nmi_window 0 0
pf_fixed 16936 0
pf_guest 0 0
remote_tlb_flush 5 0
request_irq 0 0
request_nmi 0 0
signal_exits 1 0
tlb_flush 112 0
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