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Rusty Russell authored
virtio_ring has the ability to suppress notifications. This prevents a guest exit for every packet, but we need to set a timer on packet receipt to re-check if there were any remaining packets. Here are the times for 1G TCP Guest->Host with different timeout settings (it matters because the TCP window doesn't grow big enough to fill the entire buffer): Timeout value Seconds Xmit/Recv/Timeout None (before) 25.3784 xmit 7750233 recv 1 2500 usec 62.5119 xmit 207020 recv 2 timeout 207020 1000 usec 34.5379 xmit 207003 recv 2 timeout 207003 750 usec 29.2305 xmit 207002 recv 1 timeout 207002 500 usec 19.1887 xmit 561141 recv 1 timeout 559657 250 usec 20.0465 xmit 214128 recv 2 timeout 214110 100 usec 19.2583 xmit 561621 recv 1 timeout 560153 (Note that these values are sensitive to the GSO patches which come later, and probably other traffic-related variables, so take with a large grain of salt). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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