RE: [PATCH 2/2 net-next] hyperv: Support batched notification

[KY Srinivasan <kys@microsoft.com>]

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> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Tuesday, March 10, 2015 8:34 PM
> To: KY Srinivasan
> Cc: davem@davemloft.net; netdev@vger.kernel.org;
> gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com; KY
> Srinivasan
> Subject: Re: [PATCH 2/2 net-next] hyperv: Support batched notification
> 
> 
> 
> On Wed, Mar 11, 2015 at 2:50 AM, K. Y. Srinivasan <kys@microsoft.com>
> wrote:
> > Optimize notifying the host by deferring notification until there are
> > no more packets to be sent. This will help in batching the requests on
> > the host.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > ---
> >  drivers/net/hyperv/hyperv_net.h   |    2 +-
> >  drivers/net/hyperv/netvsc.c       |   14 +++++++++-----
> >  drivers/net/hyperv/netvsc_drv.c   |    3 ++-
> >  drivers/net/hyperv/rndis_filter.c |    2 +-
> >  4 files changed, 13 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/hyperv_net.h
> > b/drivers/net/hyperv/hyperv_net.h index 4815843..3fd9896 100644
> > --- a/drivers/net/hyperv/hyperv_net.h
> > +++ b/drivers/net/hyperv/hyperv_net.h
> > @@ -184,7 +184,7 @@ struct rndis_device {  int
> > netvsc_device_add(struct hv_device *device, void *additional_info);
> > int netvsc_device_remove(struct hv_device *device);  int
> > netvsc_send(struct hv_device *device,
> > -		struct hv_netvsc_packet *packet);
> > +		struct hv_netvsc_packet *packet, bool kick_q);
> >  void netvsc_linkstatus_callback(struct hv_device *device_obj,
> >  				struct rndis_message *resp);
> >  int netvsc_recv_callback(struct hv_device *device_obj, diff --git
> > a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c index
> > 208eb05..9003b94 100644
> > --- a/drivers/net/hyperv/netvsc.c
> > +++ b/drivers/net/hyperv/netvsc.c
> > @@ -707,7 +707,7 @@ static u32 netvsc_copy_to_send_buf(struct
> > netvsc_device *net_device,  }
> >
> >  int netvsc_send(struct hv_device *device,
> > -			struct hv_netvsc_packet *packet)
> > +			struct hv_netvsc_packet *packet, bool kick_q)
> >  {
> >  	struct netvsc_device *net_device;
> >  	int ret = 0;
> > @@ -719,6 +719,7 @@ int netvsc_send(struct hv_device *device,
> >  	u32 msg_size = 0;
> >  	struct sk_buff *skb = NULL;
> >  	u16 q_idx = packet->q_idx;
> > +	u32 vmbus_flags =
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
> >
> >
> >  	net_device = get_outbound_net_device(device); @@ -768,18
> +769,21 @@
> > int netvsc_send(struct hv_device *device,
> >  		return -ENODEV;
> >
> >  	if (packet->page_buf_cnt) {
> > -		ret = vmbus_sendpacket_pagebuffer(out_channel,
> > +		ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
> >  						  packet->page_buf,
> >  						  packet->page_buf_cnt,
> >  						  &sendMessage,
> >  						  sizeof(struct
> nvsp_message),
> > -						  req_id);
> > +						  req_id,
> > +						  vmbus_flags,
> > +						  kick_q);
> 
> What if kick_q is false but ret is -EAGAIN here? Looks like in this case host
> won't get notified at all. How about checking whether txq and kicking if it has
> been stopped like what other network driver did?

Good point. I am going to fix this issue in the VMBUS layer. The kick_q argument
is simply a hint to the vmbus level - the lower level can choose not to notify the
host (even if kick_q is true) based on other considerations.

I will resend this series with the logic in the vmbus driver. I will send the patch out
and Greg can decide if the vmbus change should go through Greg's tree or David's tree.

Regards,

K. Y
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