Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754825AbaDGGGz (ORCPT ); Mon, 7 Apr 2014 02:06:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:24378 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750916AbaDGGGw (ORCPT ); Mon, 7 Apr 2014 02:06:52 -0400 Date: Mon, 7 Apr 2014 08:06:20 +0200 From: Igor Mammedov To: gaowanlong@cn.fujitsu.com Cc: Jason Wang , linux-kernel@vger.kernel.org, Rusty Russell , "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [RFC PATCH] virtio-net: reset virtqueue affinity when doing cpu hotplug Message-ID: <20140407080620.38f8bcf2@nial.usersys.redhat.com> In-Reply-To: <50DBC3E2.4090804@cn.fujitsu.com> References: <1356505614-16683-1-git-send-email-gaowanlong@cn.fujitsu.com> <50DACC26.7050409@redhat.com> <50DACF22.5090707@cn.fujitsu.com> <50DBC07B.7060303@redhat.com> <50DBC3E2.4090804@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 27 Dec 2012 11:43:30 +0800 Wanlong Gao wrote: > On 12/27/2012 11:28 AM, Jason Wang wrote: > > On 12/26/2012 06:19 PM, Wanlong Gao wrote: > >> On 12/26/2012 06:06 PM, Jason Wang wrote: > >>> On 12/26/2012 03:06 PM, Wanlong Gao wrote: > >>>> Add a cpu notifier to virtio-net, so that we can reset the > >>>> virtqueue affinity if the cpu hotplug happens. It improve > >>>> the performance through enabling or disabling the virtqueue > >>>> affinity after doing cpu hotplug. > >>> Hi Wanlong: > >>> > >>> Thanks for looking at this. > >>>> Cc: Rusty Russell > >>>> Cc: "Michael S. Tsirkin" > >>>> Cc: Jason Wang > >>>> Cc: virtualization@lists.linux-foundation.org > >>>> Cc: netdev@vger.kernel.org > >>>> Signed-off-by: Wanlong Gao > >>>> --- > >>>> drivers/net/virtio_net.c | 39 ++++++++++++++++++++++++++++++++++++++- > >>>> 1 file changed, 38 insertions(+), 1 deletion(-) > >>>> > >>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >>>> index a6fcf15..9710cf4 100644 > >>>> --- a/drivers/net/virtio_net.c > >>>> +++ b/drivers/net/virtio_net.c > >>>> @@ -26,6 +26,7 @@ > >>>> #include > >>>> #include > >>>> #include > >>>> +#include > >>>> > >>>> static int napi_weight = 128; > >>>> module_param(napi_weight, int, 0444); > >>>> @@ -34,6 +35,8 @@ static bool csum = true, gso = true; > >>>> module_param(csum, bool, 0444); > >>>> module_param(gso, bool, 0444); > >>>> > >>>> +static bool cpu_hotplug = false; > >>>> + > >>>> /* FIXME: MTU in config. */ > >>>> #define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN) > >>>> #define GOOD_COPY_LEN 128 > >>>> @@ -1041,6 +1044,26 @@ static void virtnet_set_affinity(struct virtnet_info *vi, bool set) > >>>> vi->affinity_hint_set = false; > >>>> } > >>>> > >>>> +static int virtnet_cpu_callback(struct notifier_block *nfb, > >>>> + unsigned long action, void *hcpu) > >>>> +{ > >>>> + switch(action) { > >>>> + case CPU_ONLINE: > >>>> + case CPU_ONLINE_FROZEN: > >>>> + case CPU_DEAD: > >>>> + case CPU_DEAD_FROZEN: > >>>> + cpu_hotplug = true; > >>>> + break; > >>>> + default: > >>>> + break; > >>>> + } > >>>> + return NOTIFY_OK; > >>>> +} > >>>> + > >>>> +static struct notifier_block virtnet_cpu_notifier = { > >>>> + .notifier_call = virtnet_cpu_callback, > >>>> +}; > >>>> + > >>>> static void virtnet_get_ringparam(struct net_device *dev, > >>>> struct ethtool_ringparam *ring) > >>>> { > >>>> @@ -1131,7 +1154,14 @@ static int virtnet_change_mtu(struct net_device *dev, int new_mtu) > >>>> */ > >>>> static u16 virtnet_select_queue(struct net_device *dev, struct sk_buff *skb) > >>>> { > >>>> - int txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : > >>>> + int txq; > >>>> + > >>>> + if (unlikely(cpu_hotplug == true)) { > >>>> + virtnet_set_affinity(netdev_priv(dev), true); > >>>> + cpu_hotplug = false; > >>>> + } > >>>> + > >>> Why don't you just do this in callback? > >> Callback can just give us a "hcpu", can't get the virtnet_info from callback. Am I missing something? > > > > Well, I think you can just embed the notifier block into virtnet_info, > > then use something like container_of in the callback to make the > > notifier per device. This also solve the concern of Eric. > > Yeah, thank you very much for your suggestion. I'll try it. > > >>> btw. Does qemu/kvm support cpu-hotplug now? > >> From http://www.linux-kvm.org/page/CPUHotPlug, I saw that qemu-kvm can support hotplug > >> but failed to merge to qemu.git, right? > > > > Not sure, I just try latest qemu, it even does not have a cpu_set command. > > Adding Igor to CC, > > As I know, hotplug support is cleaned from qemu, and Igor want to rework it but not been completed? > I'm not sure about that, Igor, could you send out your tech-preview-patches? CPU hot-add is supported by upstream now, hot-remove is not supported yet, besides of qemu work it would require quite a work on kvm side as well. > > Thanks, > Wanlong Gao > > > > > Thanks > >> > >> Thanks, > >> Wanlong Gao > >> > > > > > -- 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/