Some guests do a large number of mask/unmask
calls which currently trigger expensive route update
system calls.
Detect that route in unchanged and skip the system call.
Reported-by: N"Zhanghaoyu (A)" <haoyu.zhang@huawei.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>