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Date: Mon, 31 Aug 2015 10:45:57 +0800 From: Jason Wang <jasowang@...hat.com> To: vyasevic@...hat.com, "Michael S. Tsirkin" <mst@...hat.com> CC: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Patrick McHardy <kaber@...sh.net> Subject: Re: [PATCH net-next] macvtap/macvlan: use IFF_NO_QUEUE 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 <kaber@...sh.net> >>>>>>>>> >>>>>>>> Cc: Vladislav Yasevich <vyasevic@...hat.com> >>>>>>>>> >>>>>>>> Cc: Michael S. Tsirkin <mst@...hat.com> >>>>>>>>> >>>>>>>> Signed-off-by: Jason Wang <jasowang@...hat.com> >>>>>>> >>>>>> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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