Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752170AbbH1MZ5 (ORCPT ); Fri, 28 Aug 2015 08:25:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44468 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751844AbbH1MZ4 (ORCPT ); Fri, 28 Aug 2015 08:25:56 -0400 Message-ID: <55E05352.9040808@redhat.com> Date: Fri, 28 Aug 2015 08:25:54 -0400 From: Vlad Yasevich Reply-To: vyasevic@redhat.com Organization: Red Hat User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Jason Wang , "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> In-Reply-To: <55DFCA7B.8050908@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 Content-Length: 3306 Lines: 74 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 > >> >>> 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 >> My concern is that the moment someone configures a non-standard qdisc >> scalability suddenly disappears. That would also be tricky to debug in the >> field as not a lot of developers use non-standard qdiscs. >> What do you think? > > Probably not an issue. Non-standard qdisc may need be attached manually > after device creation, and we don't lose this ability with this patch. > (Unless somebody changes default_qdisc). Actually, user before > 6acf54f1cf0a6747bac9fea26f34cfc5a9029523 does not expect any qdisc work > for macvtap like other stacked devices. This patch also restore this. > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/