On Fri, Jul 11, 2014 at 01:05:30AM +0000, Wangkai (Kevin,C) wrote: > When used a tap as net driver for vm, if too many packets was delivered to > the > guest os via tap interface, the guest os will be blocked on io events for a > long > time, while tap driver was busying process packets. > > kvm vcpu thread block on io lock call trace: > __lll_lock_wait > _L_lock_1004 > __pthread_mutex_lock > qemu_mutex_lock > kvm_cpu_exec > qemu_kvm_cpu_thread_fn > start_thread > > qemu io thread call trace: > ... > qemu_net_queue_send > tap_send > qemu_iohandler_poll > main_loop_wait > main_loop > > > I think the qemu io lock time should be as small as possible, and the io work > slice should be limited at a particular ration or time. > > --- > Signed-off-by: Wangkai <wangka...@huawei.com>
How many packets are you seeing in a single tap_send() call? Have you profiled the tap_send() code path? Maybe it is performing some operation that is very slow. By the way, if you want good performance you should use vhost_net instead of userspace vhost_net. Userspace virtio-net is not very optimized. Stefan
pgpfFs1srA2wz.pgp
Description: PGP signature
