From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: [net-next PATCH V2 2/3] pktgen: avoid expensive set_current_state() call in loop Date: Thu, 26 Jun 2014 13:16:49 +0200 Message-ID: <20140626111632.23576.46982.stgit@dragon> References: <20140626111549.23576.90201.stgit@dragon> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Daniel Borkmann , Florian Westphal , Hannes Frederic Sowa , Thomas Graf , Eric Dumazet , zoltan.kiss@citrix.com, Alexander Duyck , Jeff Kirsher To: Jesper Dangaard Brouer , "David S. Miller" , netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:26006 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756853AbaFZLRV (ORCPT ); Thu, 26 Jun 2014 07:17:21 -0400 In-Reply-To: <20140626111549.23576.90201.stgit@dragon> Sender: netdev-owner@vger.kernel.org List-ID: 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 --- net/core/pktgen.c | 9 +++------ 1 files changed, 3 insertions(+), 6 deletions(-) diff --git a/net/core/pktgen.c b/net/core/pktgen.c index fc17a9d..b61f553 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);