Avi Kivity wrote: > On 10/23/2009 12:06 AM, Alexander Graf wrote: >> >> Am 22.10.2009 um 18:29 schrieb Avi Kivity <a...@redhat.com>: >> >>> On 10/13/2009 08:35 AM, Jan Kiszka wrote: >>>> It can be particularly slow if you use in-kernel irqchips and the >>>> default NIC emulation (up to 10 times slower), some effect I always >>>> wanted to understand on a rainy day. So, when you actually want -net >>>> user, try -no-kvm-irqchip. >>>> >>> >>> This might be due to a missing SIGIO or SIGALRM; -no-kvm-irqchip >>> generates a lot of extra signals and thus polling opportunities. >> >> Isn't that what dedicated io threads are supposed to solve? >> > > No. Dedicated I/O threads provide parallelism. All latency needs is to > have SIGIO sent on all file descriptors (or rather, in qemu-kvm with > irqchip, to have all file descriptors in the poll() call). > > Jan, does slirp add new connections to the select set? >
It should do so in slirp_select_fill (it iterates over all TCP&UDP sockets of all instances). I think without doing this, slirp wouldn't receive a single bit at all (no activity without FD_ISSET). Jan
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