On Tue, Oct 22, 2019 at 4:11 PM Cong Wang <xiyou.wangc...@gmail.com> wrote: > > Currently RTO, TLP and PROBE0 all share a same timer instance > in kernel and use icsk->icsk_pending to dispatch the work. > This causes spinlock contention when resetting the timer is > too frequent, as clearly shown in the perf report: > > 61.72% 61.71% swapper [kernel.kallsyms] > [k] queued_spin_lock_slowpath > ... > - 58.83% tcp_v4_rcv > - 58.80% tcp_v4_do_rcv > - 58.80% tcp_rcv_established > - 52.88% __tcp_push_pending_frames > - 52.88% tcp_write_xmit > - 28.16% tcp_event_new_data_sent > - 28.15% sk_reset_timer > + mod_timer > - 24.68% tcp_schedule_loss_probe > - 24.68% sk_reset_timer > + 24.68% mod_timer > > This patch decouples TLP timer from RTO timer by adding a new > timer instance but still uses icsk->icsk_pending to dispatch, > in order to minimize the risk of this patch. > > After this patch, the CPU time spent in tcp_write_xmit() reduced > down to 10.92%.
What is the exact benchmark you are running ? We never saw any contention like that, so lets make sure you are not working around another issue.
