From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: [net-next PATCH 4/5] pktgen: avoid expensive set_current_state() call in loop Date: Wed, 14 May 2014 16:17:59 +0200 Message-ID: <20140514141758.20309.52217.stgit@dragon> References: <20140514141545.20309.28343.stgit@dragon> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Alexander Duyck , Jeff Kirsher , Daniel Borkmann , Florian Westphal , "David S. Miller" , Stephen Hemminger , "Paul E. McKenney" , Robert Olsson , Ben Greear , John Fastabend , danieltt@kth.se, zhouzhouyi@gmail.com To: Jesper Dangaard Brouer , netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:20437 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752790AbaENOSW (ORCPT ); Wed, 14 May 2014 10:18:22 -0400 In-Reply-To: <20140514141545.20309.28343.stgit@dragon> Sender: netdev-owner@vger.kernel.org List-ID: I request review as I'm uncertain of this change as I don't know the API of set_current_state() very well. The set_current_state(TASK_INTERRUPTIBLE) uses a xchg, which implicit is LOCK prefixed. Avoid calling set_current_state() inside the busy-loop in pktgen_thread_worker(). In case of pkt_dev->delay, then it is still used in pktgen_xmit() via the spin() call. Performance data with CLONE_SKB==100000 and TX ring buffer size=1024: (single CPU performance, ixgbe 10Gbit/s, E5-2630) * Prev: 5608781 pps --> 178.29ns (1/5608781*10^9) * Now: 5857065 pps --> 170.73ns (1/5857065*10^9) * Diff: +248284 pps --> -7.56ns 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 7752806..cae7e0c 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -3409,10 +3409,10 @@ 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); @@ -3426,8 +3426,6 @@ static int pktgen_thread_worker(void *arg) continue; } - __set_current_state(TASK_RUNNING); - if (likely(pkt_dev)) { pktgen_xmit(pkt_dev); @@ -3458,9 +3456,8 @@ 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);