On 05/09/2010 10:35 PM, Gerhard Wiesinger wrote:
Please run kvm_stat and report output for both tests to confirm.
See below. 2nd column is per second statistic when running the test.
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
This indicates that kvm is emulating instead of direct mapping.
That's probably a bug. If you fix it, performance will increase
dramatically.
Where can I start here?
Any ideas how to?
One of my ideas: Move hw/vga.c functions
vga_mem_readb
vga_mem_readw
vga_mem_readl
vga_mem_writeb
vga_mem_writew
vga_mem_writel
to KVM to avoid switching from KVM to QEMU (I can write C code even
kernel but I'm not comfortable with KVM). Howto?
That is already done (generically), it's called coalesced mmio. You
only have 3470 qemu exits/sec compared to 554244 kvm writes/sec.
Switching between tcg and kvm is hard, but not needed. For 256 color
modes, direct map is possible and should yield good performance.
Bank switching can be improved perhaps 3x, but will never be fast.
Where can I start for KVM performance for the bank switching (256
color mode)? (e.g. BIOS writes to VGA window I/O port to switch the bank)
Any ideas how to improve (architecture for the change)?
For 256 color more the first priority is to find out why direct mapping
is not used. I'd suggest tracing the code that makes this decision (in
hw/*vga.c) and seeing if it's right or not.
--
error compiling committee.c: too many arguments to function
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