From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH] get 2% or more performance improved by reducing spin_lock race Date: Fri, 07 Jun 2013 16:50:35 +0800 Message-ID: <51B19EDB.5040604@redhat.com> References: <5872DA217C2FF7488B20897D84F904E7339109CE@nkgeml511-mbx.china.huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: "mst@redhat.com" , "rusty@rustcorp.com.au" , "(kvm@vger.kernel.org)" , "(netdev@vger.kernel.org)" , Heguansen To: Qinchuanyu Return-path: Received: from mx1.redhat.com ([209.132.183.28]:63930 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753172Ab3FGIvP (ORCPT ); Fri, 7 Jun 2013 04:51:15 -0400 In-Reply-To: <5872DA217C2FF7488B20897D84F904E7339109CE@nkgeml511-mbx.china.huawei.com> Sender: netdev-owner@vger.kernel.org List-ID: On 06/07/2013 03:31 PM, Qinchuanyu wrote: > the wake_up_process func is included by spin_lock/unlock in vhost_work_queue, > but it could be done outside the spin_lock. > I have test it with kernel 3.0.27 and guest suse11-sp2 using iperf, the num as below. > orignal modified > thread_num tp(Gbps) vhost(%) | tp(Gbps) vhost(%) > 1 9.59 28.82 | 9.59 27.49 > 8 9.61 32.92 | 9.62 26.77 > 64 9.58 46.48 | 9.55 38.99 > 256 9.6 63.7 | 9.6 52.59 > > Signed-off-by: Chuanyu Qin > --- > drivers/vhost/vhost.c | 5 +++-- > 1 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 94dbd25..8bee109 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -146,9 +146,10 @@ static inline void vhost_work_queue(struct vhost_dev *dev, > if (list_empty(&work->node)) { > list_add_tail(&work->node, &dev->work_list); > work->queue_seq++; > + spin_unlock_irqrestore(&dev->work_lock, flags); > wake_up_process(dev->worker); > - } > - spin_unlock_irqrestore(&dev->work_lock, flags); > + } else > + spin_unlock_irqrestore(&dev->work_lock, flags); > } > > void vhost_poll_queue(struct vhost_poll *poll) Hi Chuanyu: I believe you need a better name of the patch such as: vhost: wake up worker outside spinlock