• Asias He's avatar
    kvm tools: Respect ISR status in virtio header · 7f5ffaf5
    Asias He authored
    
    
    Inject IRQ to guest only when ISR status is low which means
    guest has read ISR status and device has cleared this bit as
    the side effect of this reading.
    
    This reduces a lot of unnecessary IRQ inject from device to
    guest.
    
    Netpef test shows this patch changes:
    
    the host to guest bandwidth
    from 2866.27 Mbps (cpu 33.96%) to 5548.87 Mbps (cpu 53.87%),
    
    the guest to host bandwitdth
    form 1408.86 Mbps (cpu 99.9%) to 1301.29 Mbps (cpu 99.9%).
    
    The bottleneck of the guest to host bandwidth is guest cpu power.
    
    Signed-off-by: default avatarAsias He <asias.hejun@gmail.com>
    Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
    7f5ffaf5