diff options
| author |   Shachar Raindel <shacharr@microsoft.com> | 2021-03-12 15:45:27 -0800 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2021-03-14 14:32:37 -0700 |
| commit | bd49fea7586b9d39a38846e9ef4ac056e4eb6e59 (patch) | |
| tree | 2f24bccd2826e7b7080342dbeaf9e40c73a29c3c /drivers/net/hyperv | |
| parent | Merge branch 'pktgen-scripts-improvements' (diff) | |
| download | wireguard-linux-bd49fea7586b9d39a38846e9ef4ac056e4eb6e59.tar.xz wireguard-linux-bd49fea7586b9d39a38846e9ef4ac056e4eb6e59.zip | |
hv_netvsc: Add a comment clarifying batching logic
The batching logic in netvsc_send is non-trivial, due to
a combination of the Linux API and the underlying hypervisor
interface. Add a comment explaining why the code is written this
way.
Signed-off-by: Shachar Raindel <shacharr@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/hyperv')
| -rw-r--r-- | drivers/net/hyperv/netvsc.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c index c64cc7639c39..5bce24731502 100644 --- a/drivers/net/hyperv/netvsc.c +++ b/drivers/net/hyperv/netvsc.c @@ -1017,6 +1017,26 @@ static inline void move_pkt_msd(struct hv_netvsc_packet **msd_send, } /* RCU already held by caller */ +/* Batching/bouncing logic is designed to attempt to optimize + * performance. + * + * For small, non-LSO packets we copy the packet to a send buffer + * which is pre-registered with the Hyper-V side. This enables the + * hypervisor to avoid remapping the aperture to access the packet + * descriptor and data. + * + * If we already started using a buffer and the netdev is transmitting + * a burst of packets, keep on copying into the buffer until it is + * full or we are done collecting a burst. If there is an existing + * buffer with space for the RNDIS descriptor but not the packet, copy + * the RNDIS descriptor to the buffer, keeping the packet in place. + * + * If we do batching and send more than one packet using a single + * NetVSC message, free the SKBs of the packets copied, except for the + * last packet. This is done to streamline the handling of the case + * where the last packet only had the RNDIS descriptor copied to the + * send buffer, with the data pointers included in the NetVSC message. + */ int netvsc_send(struct net_device *ndev, struct hv_netvsc_packet *packet, struct rndis_message *rndis_msg, |