[Xen-devel] Reducing I/O introduced domain scheduling

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

Keir:
        When running vConsolidation on top of Xen in  a 4-core platform, we 
noticed the I/O introduced scheduling per CPU is ~3K Hz, which seems to be too 
frequent and cause frequent involve of domain 0 / Qemu, which may polute cache 
of the guest and thus increase CPI (cycle per instruction).

        We are thinking if we can reduce the domin switch here, and think the 
output of I/O can be buffered and return immediately. The buffered I/O can be 
flushed out at next IN emulation (or any Hypervisor emulated I/O) or timeout 
such as 10 or 100 us to guarantee minimal response.

        Ideally it can cover both PIO & MMIO, but we can start from PIO.

        How do you think of that?

Thx, Eddie
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