From: Jesper Dangaard Brouer Date: Thu, 26 Jun 2014 11:16:49 +0000 (+0200) Subject: pktgen: avoid expensive set_current_state() call in loop X-Git-Tag: firefly_0821_release~176^2~3474^2~246^2~1 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=baac167b706600ebe7158acaeb7c489ae9d0bb8b;p=firefly-linux-kernel-4.4.55.git pktgen: avoid expensive set_current_state() call in loop Avoid calling set_current_state() inside the busy-loop in pktgen_thread_worker(). In case of pkt_dev->delay, then it is still used/enabled in pktgen_xmit() via the spin() call. The set_current_state(TASK_INTERRUPTIBLE) uses a xchg, which implicit is LOCK prefixed. I've measured the asm LOCK operation to take approx 8ns on this E5-2630 CPU. Performance increase corrolate with this measurement. Performance data with CLONE_SKB==100000, rx-usecs=30: (single CPU performance, ixgbe 10Gbit/s, E5-2630) * Prev: 5454050 pps --> 183.35ns (1/5454050*10^9) * Now: 5684009 pps --> 175.93ns (1/5684009*10^9) * Diff: +229959 pps --> -7.42ns Signed-off-by: Jesper Dangaard Brouer Signed-off-by: David S. Miller --- diff --git a/net/core/pktgen.c b/net/core/pktgen.c index fc17a9d309ac..b61f553689b6 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -3407,10 +3407,10 @@ static int pktgen_thread_worker(void *arg) pr_debug("starting pktgen/%d: pid=%d\n", cpu, task_pid_nr(current)); - set_current_state(TASK_INTERRUPTIBLE); - set_freezable(); + __set_current_state(TASK_RUNNING); + while (!kthread_should_stop()) { pkt_dev = next_to_run(t); @@ -3424,8 +3424,6 @@ static int pktgen_thread_worker(void *arg) continue; } - __set_current_state(TASK_RUNNING); - if (likely(pkt_dev)) { pktgen_xmit(pkt_dev); @@ -3456,9 +3454,8 @@ static int pktgen_thread_worker(void *arg) } try_to_freeze(); - - set_current_state(TASK_INTERRUPTIBLE); } + set_current_state(TASK_INTERRUPTIBLE); pr_debug("%s stopping all device\n", t->tsk->comm); pktgen_stop(t);