On Sun, Dec 18, 2005 at 11:28:27PM +0000, Paul Brook wrote: > Dan mentioned he was seeing very poor network performance when using > user-net. > It turns out this is because packets were getting dropped (the NIC buffers > were full), and the slirp code doesn't throttle properly when this occurs. > You end up with a bunch of packets getting sent to the guest, half of which > get dropped, then a delay until slirp retransmits. > > This is much more noticeable on Arm because the NIC only has a small memory > buffer. > > Teaching the slirp code how to do tcp backoff/window scaling is probably a > fair amount of work. The easy alternative is to throttle the slirp output > when we know the card's buffers are full. slirp has a convenient hook for > this, so it's a matter of adding the hooks to the hardware emulation. > > This increases arm user-net performance from painfully slow (~200kbit) to > guest CPU bound (~20Mbit). > Hmm is the patch supposed to work for i386 guests too? I get no dhcp response and network unreachable when i try to ssh to the host from the guest after manually ifconfig'ing, seem like the ne2k doesn't receive any packets. (FreeBSD/i386 host, linux i386 guest - kanotix livecd iso). The same works normally without the patch.
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