From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752389AbbHaCqF (ORCPT ); Sun, 30 Aug 2015 22:46:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47088 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751981AbbHaCqD (ORCPT ); Sun, 30 Aug 2015 22:46:03 -0400 Message-ID: <55E3BFE5.2080208@redhat.com> Date: Mon, 31 Aug 2015 10:45:57 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: vyasevic@redhat.com, "Michael S. Tsirkin" CC: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Patrick McHardy Subject: Re: [PATCH net-next] macvtap/macvlan: use IFF_NO_QUEUE References: <1440405192-25926-1-git-send-email-jasowang@redhat.com> <20150825131608-mutt-send-email-mst@redhat.com> <55DC51C1.5090201@redhat.com> <55DC98A3.7010601@redhat.com> <55DD527A.8040806@redhat.com> <20150827134102-mutt-send-email-mst@redhat.com> <55DFCA7B.8050908@redhat.com> <55E05352.9040808@redhat.com> In-Reply-To: <55E05352.9040808@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/28/2015 08:25 PM, Vlad Yasevich wrote: > On 08/27/2015 10:42 PM, Jason Wang wrote: >> > >> > >> > On 08/27/2015 06:43 PM, Michael S. Tsirkin wrote: >>> >> On Wed, Aug 26, 2015 at 01:45:30PM +0800, Jason Wang wrote: >>>> >>> >>>> >>> On 08/26/2015 12:32 AM, Vlad Yasevich wrote: >>>>> >>>> On 08/25/2015 07:30 AM, Jason Wang wrote: >>>>>> >>>>> On 08/25/2015 06:17 PM, Michael S. Tsirkin wrote: >>>>>>> >>>>>> On Mon, Aug 24, 2015 at 04:33:12PM +0800, Jason Wang wrote: >>>>>>>>> >>>>>>>> For macvlan, switch to use IFF_NO_QUEUE instead of tx_queue_len = 0. >>>>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>> For macvtap, after commit 6acf54f1cf0a6747bac9fea26f34cfc5a9029523 >>>>>>>>> >>>>>>>> ("macvtap: Add support of packet capture on macvtap >>>>>>>>> >>>>>>>> device."). Multiqueue macvtap suffers from single qdisc lock >>>>>>>>> >>>>>>>> contention. This is because macvtap claims a non zero tx_queue_len and >>>>>>>>> >>>>>>>> it reuses this value as it socket receive queue size.Thanks to >>>>>>>>> >>>>>>>> IFF_NO_QUEUE, we can remove the lock contention without breaking >>>>>>>>> >>>>>>>> existing socket receive queue length logic. >>>>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>> Cc: Patrick McHardy >>>>>>>>> >>>>>>>> Cc: Vladislav Yasevich >>>>>>>>> >>>>>>>> Cc: Michael S. Tsirkin >>>>>>>>> >>>>>>>> Signed-off-by: Jason Wang >>>>>>> >>>>>> Seems to make sense. Give me a day or two to get over the jet lag >>>>>>> >>>>>> (and get out from under the pile of mail accumulated while I was traveling), >>>>>>> >>>>>> I'll review properly and ack. >>>>>>> >>>>>> >>>>>> >>>>> A note on this patch: only default qdisc were removed but we don't lose >>>>>> >>>>> the ability to attach a qdisc to macvtap (though it may cause lock >>>>>> >>>>> contention on multiqueue case). >>>>>> >>>>> >>>>> >>>> Wouldn't that lock contention be solved if we really had multiple queues >>>>> >>>> for multi-queue macvtaps? >>>>> >>>> >>>>> >>>> -vlad >>>> >>> Yes, but this introduce another layer of txq locks contention? >>> >> I don't follow - why does it? Could you clarify please? >> > >> > I believe Vlad wants to remove NETIF_F_LLTX. If yes, core will do an >> > extra tx lock at macvlan layer. > No, I don't want to remove it. In a sense, it would function similar to > how it works when fwd_priv is populated. I am still testing the code > as it's showing some strange artifacts... could be due to keeping LLTX. > > -vlad > I see. I'm ok to wait for your code. But if a patch of just two lines works, probably no need to try complex method. Thanks