From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH] vhost: get 2% performance improved by reducing spin_lock race in vhost_work_queue Date: Mon, 20 May 2013 12:46:55 +0800 Message-ID: <5199AABF.6090801@redhat.com> References: <5872DA217C2FF7488B20897D84F904E7338FD1E5@nkgeml511-mbx.china.huawei.com> <51999AA2.8070806@redhat.com> <5872DA217C2FF7488B20897D84F904E7338FD2C5@nkgeml511-mbx.china.huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "rusty@rustcorp.com.au" , "mst@redhat.com" , "dhowells@redhat.com" , "(kvm@vger.kernel.org)" , "(netdev@vger.kernel.org)" , Heguansen To: Qinchuanyu Return-path: Received: from mx1.redhat.com ([209.132.183.28]:25399 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750822Ab3ETErx (ORCPT ); Mon, 20 May 2013 00:47:53 -0400 In-Reply-To: <5872DA217C2FF7488B20897D84F904E7338FD2C5@nkgeml511-mbx.china.huawei.com> Sender: netdev-owner@vger.kernel.org List-ID: On 05/20/2013 12:22 PM, Qinchuanyu wrote: > The patch below is base on=20 > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree= /drivers/vhost/vhost.c?id=3Drefs/tags/next-20130517 > > Signed-off-by: Chuanyu Qin > --- a/drivers/vhost/vhost.c 2013-05-20 11:47:05.000000000 +0800 > +++ b/drivers/vhost/vhost.c 2013-05-20 11:48:24.000000000 +0800 > @@ -154,9 +154,10 @@ > 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); > } > =20 > void vhost_poll_queue(struct vhost_poll *poll) > > I did the test by using iperf in 10G environment, the test num as bel= ow: > 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 > > The cost of vhost reduced while the throughput is almost unchanged. Thanks, and please generate a formal patch based on Documentation/SubmittingPatches (put the description and perf numbers i= n the commit log). Then resubmit it to let the maintainer apply it. > > On 05/20/2013 11:06 AM, Qinchuanyu wrote: >> Right now the wake_up_process func is included in spin_lock/unlock, = but it could be done outside the spin_lock. >> I have test it with kernel 3.0.27 and guest suse11-sp2, it provide 2= %-3% net performance improved. >> >> Signed-off-by: Chuanyu Qin > Make sense to me but need generate a patch against net-next.git or > vhost.git in git.kernel.org. > > Btw. How did you test this? Care to share the perf numbers? > > Thanks >> mu >> --- a/drivers/vhost/vhost.c 2013-05-20 10:36:30.000000000 +0800 >> +++ b/drivers/vhost/vhost.c 2013-05-20 10:36:54.000000000 +0800 >> @@ -144,9 +144,10 @@ >> 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); >> } >> =20 >> void vhost_poll_queue(struct vhost_poll *poll) >> -- >> To unsubscribe from this list: send the line "unsubscribe netdev" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > N=EF=BF=BD=EF=BF=BD=EF=BF=BD=EF=BF=BD=EF=BF=BDr=EF=BF=BD=EF=BF=BDy=EF= =BF=BD=EF=BF=BD=EF=BF=BDb=EF=BF=BDX=EF=BF=BD=EF=BF=BD=C7=A7v=EF=BF=BD^=EF= =BF=BD)=DE=BA{.n=EF=BF=BD+=EF=BF=BD=EF=BF=BD=EF=BF=BDz=EF=BF=BD^=EF=BF=BD= )=EF=BF=BD=EF=BF=BD=EF=BF=BDw*=1Fjg=EF=BF=BD=EF=BF=BD=EF=BF=BD=1E=EF=BF= =BD=EF=BF=BD=EF=BF=BD=EF=BF=BD=EF=BF=BD=DD=A2j/=EF=BF=BD=EF=BF=BD=EF=BF= =BDz=EF=BF=BD=DE=96=EF=BF=BD=EF=BF=BD2=EF=BF=BD=DE=99=EF=BF=BD=EF=BF=BD= =EF=BF=BD&=EF=BF=BD)=DF=A1=EF=BF=BDa=EF=BF=BD=EF=BF=BD=7F=EF=BF=BD=EF=BF= =BD=1E=EF=BF=BDG=EF=BF=BD=EF=BF=BD=EF=BF=BDh=EF=BF=BD=0F=EF=BF=BDj:+v=EF= =BF=BD=EF=BF=BD=EF=BF=BDw=EF=BF=BD=D9=A5