From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net] macvtap: unbreak receiving of gro skb with frag list Date: Tue, 27 Oct 2015 11:05:50 +0200 Message-ID: <20151027110253-mutt-send-email-mst@redhat.com> References: <1445576225-27710-1-git-send-email-jasowang@redhat.com> <20151023163659-mutt-send-email-mst@redhat.com> <562D9AED.4060607@redhat.com> <20151026080851-mutt-send-email-mst@redhat.com> <562DCDF2.6030305@redhat.com> <20151026102928-mutt-send-email-mst@redhat.com> <562EE851.40605@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Vlad Yasevich To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <562EE851.40605@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Oct 27, 2015 at 10:58:25AM +0800, Jason Wang wrote: > > > On 10/26/2015 04:30 PM, Michael S. Tsirkin wrote: > > On Mon, Oct 26, 2015 at 02:53:38PM +0800, Jason Wang wrote: > >> > >> On 10/26/2015 02:09 PM, Michael S. Tsirkin wrote: > >>> On Mon, Oct 26, 2015 at 11:15:57AM +0800, Jason Wang wrote: > >>>> On 10/23/2015 09:37 PM, Michael S. Tsirkin wrote: > >>>>> On Fri, Oct 23, 2015 at 12:57:05AM -0400, Jason Wang wrote: > >>>>>> We don't have fraglist support in TAP_FEATURES. This will lead > >>>>>> software segmentation of gro skb with frag list. Fixes by having > >>>>>> frag list support in TAP_FEATURES. > >>>>>> > >>>>>> With this patch single session of netperf receiving were restored from > >>>>>> about 5Gb/s to about 12Gb/s on mlx4. > >>>>>> > >>>>>> Fixes a567dd6252 ("macvtap: simplify usage of tap_features") > >>>>>> Cc: Vlad Yasevich > >>>>>> Cc: Michael S. Tsirkin > >>>>>> Signed-off-by: Jason Wang > >>>>> Thanks! > >>>>> Does this mean we should look at re-adding NETIF_F_FRAGLIST > >>>>> to virtio-net as well? > >>>> Not sure I get the point, but probably not. This is for receiving and > >>>> skb_copy_datagram_iter() can deal with frag list. > >>> Point is: > >>> - bridge within guest > >>> - assigned device creating gro skbs with frag list bridged to virtio > >> I see, but this problem looks not specific to virtio. Most cards does > >> not support frag list. > > These will be slower when used with a bridge then, won't they? > > For forwarding, not sure. GRO has latency and cpu overhead anyway. Right but that's up to the user. You aren't disabling GRO on source, you are just splitting it up. > Anyway I can try to add the support for this. Which reminds me: on modern devices there are commands to control offloads, so for these, we should support turning offloads on/off using ethtool. -- MST