On Thu, Sep 13, 2018 at 1:40 AM Jason Wang <jasowang@xxxxxxxxxx> wrote: > > Implement ethtool .set_coalesce (-C) and .get_coalesce (-c) handlers. > Interrupt moderation is currently not supported, so these accept and > display the default settings of 0 usec and 1 frame. > > Toggle tx napi through a bit in tx-frames. So as to not interfere > with possible future interrupt moderation, value 1 means tx napi while > value 0 means not. > > To properly synchronize with the data path, tx napi is disabled and > tx lock is held when changing the value of napi weight. And two more > places that can access tx napi weight: > > - speculative tx polling in rx napi, we can leave it as is since it > not a must for correctness. > - skb_xmit_done(), one more check of napi weight is added before > trying to enable tx to avoid tx to be disabled forever if napi is > disabled after skb_xmit_done() but before the napi > > Link: https://patchwork.ozlabs.org/patch/948149/ > Suggested-by: Jason Wang <jasowang@xxxxxxxxxx> > Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx> > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx> > --- > Changes from V1: > - try to synchronize with datapath to allow changing mode when > interface is up. > - use tx-frames 0 as to disable tx napi while tx-frames 1 to enable tx napi > --- > drivers/net/virtio_net.c | 64 +++++++++++++++++++++++++++++++++++++++- > 1 file changed, 63 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 765920905226..6e70864f5899 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -66,6 +66,8 @@ DECLARE_EWMA(pkt_len, 0, 64) > > #define VIRTNET_DRIVER_VERSION "1.0.0" > > +static const u32 ethtool_coalesce_napi_mask = (1UL << 10); > + This is no longer needed > static const unsigned long guest_offloads[] = { > VIRTIO_NET_F_GUEST_TSO4, > VIRTIO_NET_F_GUEST_TSO6, > @@ -1444,7 +1446,10 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) > > virtqueue_napi_complete(napi, sq->vq, 0); > > - if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) > + /* Check napi.weight to avoid tx stall since it could be set > + * to zero by ethtool after skb_xmit_done(). > + */ > + if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS || !sq->napi.weight) > netif_tx_wake_queue(txq); I see. This assumes that the napi handler will always be called on conversion from napi to no-napi mode. That is safe to assume because if it isn't called (and will not call netif_tx_wake_queue) that implies that napi was not scheduled, and thus the tx interrupt was not suppressed and thus there was no tx completion work to be scheduled? > > return 0; > @@ -2181,6 +2186,61 @@ static int virtnet_get_link_ksettings(struct net_device *dev, > return 0; > } > > +static int virtnet_set_coalesce(struct net_device *dev, > + struct ethtool_coalesce *ec) > +{ > + struct ethtool_coalesce ec_default = { > + .cmd = ETHTOOL_SCOALESCE, > + .rx_max_coalesced_frames = 1, > + }; > + struct virtnet_info *vi = netdev_priv(dev); > + int i, napi_weight; > + > + if (ec->tx_max_coalesced_frames > 1) > + return -EINVAL; > + > + ec_default.tx_max_coalesced_frames = ec->tx_max_coalesced_frames; > + napi_weight = ec->tx_max_coalesced_frames ? NAPI_POLL_WEIGHT : 0; > + > + /* disallow changes to fields not explicitly tested above */ > + if (memcmp(ec, &ec_default, sizeof(ec_default))) > + return -EINVAL; > + > + if (napi_weight ^ vi->sq[0].napi.weight) { > + for (i = 0; i < vi->max_queue_pairs; i++) { > + struct netdev_queue *txq = > + netdev_get_tx_queue(vi->dev, i); > + > + virtnet_napi_tx_disable(&vi->sq[i].napi); > + __netif_tx_lock_bh(txq); > + vi->sq[i].napi.weight = napi_weight; > + __netif_tx_unlock_bh(txq); > + virtnet_napi_tx_enable(vi, vi->sq[i].vq, > + &vi->sq[i].napi); > + } > + } > + > + return 0; > +} > + > +static int virtnet_get_coalesce(struct net_device *dev, > + struct ethtool_coalesce *ec) > +{ > + struct ethtool_coalesce ec_default = { > + .cmd = ETHTOOL_GCOALESCE, > + .rx_max_coalesced_frames = 1, > + .tx_max_coalesced_frames = 0, no need to explicitly initialize to 0 (unless you did this for documentation purposes, which is fine). > + }; > + struct virtnet_info *vi = netdev_priv(dev); > + > + memcpy(ec, &ec_default, sizeof(ec_default)); > + > + if (vi->sq[0].napi.weight) > + ec->tx_max_coalesced_frames = 1; > + > + return 0; > +} > + > static void virtnet_init_settings(struct net_device *dev) > { > struct virtnet_info *vi = netdev_priv(dev); > @@ -2219,6 +2279,8 @@ static const struct ethtool_ops virtnet_ethtool_ops = { > .get_ts_info = ethtool_op_get_ts_info, > .get_link_ksettings = virtnet_get_link_ksettings, > .set_link_ksettings = virtnet_set_link_ksettings, > + .set_coalesce = virtnet_set_coalesce, > + .get_coalesce = virtnet_get_coalesce, > }; > > static void virtnet_freeze_down(struct virtio_device *vdev) > -- > 2.17.1 > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
