• Eric Dumazet's avatar
    net_sched: drop packets after root qdisc lock is released · 520ac30f
    Eric Dumazet authored
    Qdisc performance suffers when packets are dropped at enqueue()
    time because drops (kfree_skb()) are done while qdisc lock is held,
    delaying a dequeue() draining the queue.
    
    Nominal throughput can be reduced by 50 % when this happens,
    at a time we would like the dequeue() to proceed as fast as possible.
    
    Even FQ is vulnerable to this problem, while one of FQ goals was
    to provide some flow isolation.
    
    This patch adds a 'struct sk_buff **to_free' parameter to all
    qdisc->enqueue(), and in qdisc_drop() helper.
    
    I measured a performance increase of up to 12 %, but this patch
    is a prereq so that future batches in enqueue() can fly.
    Signed-off-by: 's avatarEric Dumazet <edumazet@google.com>
    Acked-by: 's avatarJesper Dangaard Brouer <brouer@redhat.com>
    Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
    520ac30f