Avi Kivity wrote:
Anthony Liguori wrote:
We don't use signalfd in upstream QEMU. Instead, we always emulate it.
With an extra thread -> so an extra context switch.
We don't use an extra thread. We just install a signal handler that
writes to a pipe. At best, the added overhead is that we get EINTRs
more often but this is something we already handle.
It's not necessarily a bad thing to use signalfd, but this is
something that
should be done upstream. It certainly does qemu-kvm no harm to use
the upstream
code.
It will introduce a (likely minor, but real) performance regression.
Instead of this, why not apply the reverse patch to qemu.git?
I'm not sure signalfd really buys us much. To emulate it requires
writing a bunch more data to the pipe. When writing more than 1 byte,
we have to worry about whether there's a partial write because the pipe
buffers full). We also have to make sure to read from the fd in
properly sized chunks.
Regards,
Anthony Liguori
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