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Message-ID: <1356537072.20133.20400.camel@edumazet-glaptop> Date: Wed, 26 Dec 2012 07:51:12 -0800 From: Eric Dumazet <erdnetdev@...il.com> To: Wanlong Gao <gaowanlong@...fujitsu.com> Cc: linux-kernel@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>, "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org Subject: Re: [RFC PATCH] virtio-net: reset virtqueue affinity when doing cpu hotplug On Wed, 2012-12-26 at 15:06 +0800, 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. > > Cc: Rusty Russell <rusty@...tcorp.com.au> > Cc: "Michael S. Tsirkin" <mst@...hat.com> > Cc: Jason Wang <jasowang@...hat.com> > Cc: virtualization@...ts.linux-foundation.org > Cc: netdev@...r.kernel.org > Signed-off-by: Wanlong Gao <gaowanlong@...fujitsu.com> > --- > 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 <linux/scatterlist.h> > #include <linux/if_vlan.h> > #include <linux/slab.h> > +#include <linux/cpu.h> > > 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; > + } > + > + txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : > smp_processor_id(); > > while (unlikely(txq >= dev->real_num_tx_queues)) > @@ -1248,6 +1278,8 @@ static void virtnet_del_vqs(struct virtnet_info *vi) > { > struct virtio_device *vdev = vi->vdev; > > + unregister_hotcpu_notifier(&virtnet_cpu_notifier); > + > virtnet_set_affinity(vi, false); > > vdev->config->del_vqs(vdev); > @@ -1372,6 +1404,11 @@ static int init_vqs(struct virtnet_info *vi) > goto err_free; > > virtnet_set_affinity(vi, true); > + > + ret = register_hotcpu_notifier(&virtnet_cpu_notifier); > + if (ret) > + goto err_free; > + > return 0; > > err_free: It looks like this patch assumes virtio_net supports a single instance. Try your patch with two instances, I am pretty sure it wont do very well. It seems to me you need something else than a single boolean. A sequence number for example should be better... -- 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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