From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH] vhost: make vhost_zerocopy_callback more efficient by poll_queue base on vhost status Date: Tue, 25 Feb 2014 15:38:08 +0800 Message-ID: <530C4860.2000402@redhat.com> References: <530C3E74.6030409@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: KVM list To: Qin Chuanyu , davem@davemloft.net, "Michael S. Tsirkin" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:31036 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751485AbaBYHiS (ORCPT ); Tue, 25 Feb 2014 02:38:18 -0500 In-Reply-To: <530C3E74.6030409@huawei.com> Sender: kvm-owner@vger.kernel.org List-ID: On 02/25/2014 02:55 PM, Qin Chuanyu wrote: > guest kick vhost base on vring flag status and get perfermance improved, > vhost_zerocopy_callback could do this in the same way, as > virtqueue_enable_cb need one more check after change the status of > avail_ring flags, vhost also do the same thing after vhost_enable_notify > > test result list as below: > guest and host: suse11sp3, netperf, intel 2.4GHz > +-------+----------+---------+----------+---------+ > | | old | new | > +-------+----------+---------+----------+---------+ > | UDP | Gbit/s | PPS | Gbit/s | PPS | > | 256 | 0.74805 | 321309 | 0.77933 | 334743 | > | 512 | 1.42 | 328475 | 1.44 | 333550 | > | 1024 | 2.79 | 334426 | 2.81 | 336986 | > | 1460 | 3.71 | 316215 | 4.02 | 342325 | > +-------+----------+---------+----------+---------+ Looks good, do you have cpu utilization number? > > Signed-off-by: Chuanyu Qin > --- > drivers/vhost/net.c | 10 +++++++++- > 1 files changed, 9 insertions(+), 1 deletions(-) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index a0fa5de..9bc0a15 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -322,7 +322,9 @@ static void vhost_zerocopy_callback(struct > ubuf_info *ubuf, bool success) > * (the value 16 here is more or less arbitrary, it's tuned to > trigger > * less than 10% of times). > */ > - if (cnt <= 1 || !(cnt % 16)) > + smp_rmb(); Better add a comment to explain why this is needed. Looks like what you need is a smp_mb() here to make sure the len is updated before testing vq->used_flags? > + if ((!(vq->used_flags & VRING_USED_F_NO_NOTIFY)) > + && (cnt <= 1 || !(cnt % 16))) > vhost_poll_queue(&vq->poll); > > rcu_read_unlock_bh(); > @@ -386,6 +388,12 @@ static void handle_tx(struct vhost_net *net) > vhost_disable_notify(&net->dev, vq); > continue; > } > + /* there might skb been freed between last > + * vhost_zerocopy_signal_used and vhost_enable_notify, > + * so one more check is needed. > + */ > + if (zcopy) > + vhost_zerocopy_signal_used(net, vq); > break; > } > if (in) {