[RFC] Multiple QEMU AIO implementations

Anthony Liguori
2008-04-16T21:36:42Z

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This isn't fully cooked yet, but pretty close. The basic idea is to
make the aio usage in block-raw go to a set of function pointers and
allow multiple simultaneous AIO implementations.

I converted the posix-aio support to this, and also introduced a "unix"
aio which just uses O_NONBLOCK and select(). The later only supports 1
simultaneous request per-fd but currently posix-aio is limited to that
too. At least with my QEMU testing, the unix aio implementation
outperforms posix-aio by a factor of 2.

And it uses no signals...

I'm inclined to suggest that we use signalfd with posix-aio, and for
older guests, just fall back to unix aio. We can also introduce a
linux-aio and use that when possible.

Regards,

Anthony Liguori

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