From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932608AbbHZFpi (ORCPT ); Wed, 26 Aug 2015 01:45:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57164 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751951AbbHZFpg (ORCPT ); Wed, 26 Aug 2015 01:45:36 -0400 Message-ID: <55DD527A.8040806@redhat.com> Date: Wed, 26 Aug 2015 13:45:30 +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> In-Reply-To: <55DC98A3.7010601@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 08/26/2015 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? And it also needs macvlan multiqueue support. We used to do something like this but switch to NETIF_F_LLTX finally. You may refer: 2c11455321f37da6fe6cc36353149f9ac9183334 macvlan: add multiqueue capability 8ffab51b3dfc54876f145f15b351c41f3f703195 macvlan: lockless tx path