On Wed, Apr 20, 2022 at 8:53 PM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: > > xiangxia.m.yue@xxxxxxxxx writes: > > > From: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx> > > > > This patch introduce a new bpf_ktime_get_real_ns helper, which may > > help us to measure the skb latency in the ingress/forwarding path: > > > > HW/SW[1] -> ip_rcv/tcp_rcv_established -> tcp_recvmsg_locked/tcp_update_recv_tstamps > > > > * Insert BPF kprobe into ip_rcv/tcp_rcv_established invoking this helper. > > Then we can inspect how long time elapsed since HW/SW. > > * If inserting BPF kprobe tcp_update_recv_tstamps invoked by tcp_recvmsg, > > we can measure how much latency skb in tcp receive queue. The reason for > > this can be application fetch the TCP messages too late. > > Why not just use one of the existing ktime helpers and also add a BPF > probe to set the initial timestamp instead of relying on skb->tstamp? Yes, That also looks good to me. > -Toke -- Best regards, Tonghao
