linux-kernel - RE: [PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag to optimize signaling the host

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Message-ID: <BN1PR0301MB070730518ED94BEFE12C2683A0D00@BN1PR0301MB0707.namprd03.prod.outlook.com>
Date:	Wed, 6 May 2015 00:08:44 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag to
 optimize signaling the host



> -----Original Message-----
> From: Eric Dumazet [mailto:eric.dumazet@...il.com]
> Sent: Thursday, April 30, 2015 9:37 PM
> To: KY Srinivasan
> Cc: davem@...emloft.net; netdev@...r.kernel.org; linux-
> kernel@...r.kernel.org; devel@...uxdriverproject.org; olaf@...fle.de;
> apw@...onical.com; jasowang@...hat.com
> Subject: Re: [PATCH V2 net-next 1/1] hv_netvsc: Use the xmit_more skb flag
> to optimize signaling the host
> 
> On Thu, 2015-04-30 at 16:29 -0700, K. Y. Srinivasan wrote:
> > Based on the information given to this driver (via the xmit_more skb flag),
> > we can defer signaling the host if more packets are on the way. This will
> help
> > make the host more efficient since it can potentially process a larger batch
> of
> > packets. Implement this optimization.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > ---
> > 	v2: Fixed up indentation based on feedback from David Miller.
> >
> >  drivers/net/hyperv/netvsc.c |   20 ++++++++++++--------
> >  1 files changed, 12 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> > index 2e8ad06..5fdc5e1 100644
> > --- a/drivers/net/hyperv/netvsc.c
> > +++ b/drivers/net/hyperv/netvsc.c
> > @@ -743,6 +743,7 @@ static inline int netvsc_send_pkt(
> >  	u64 req_id;
> >  	int ret;
> >  	struct hv_page_buffer *pgbuf;
> > +	u32 vmbus_flags =
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
> >
> >  	nvmsg.hdr.msg_type = NVSP_MSG1_TYPE_SEND_RNDIS_PKT;
> >  	if (packet->is_data_pkt) {
> > @@ -772,19 +773,22 @@ static inline int netvsc_send_pkt(
> >  	if (packet->page_buf_cnt) {
> >  		pgbuf = packet->cp_partial ? packet->page_buf +
> >  			packet->rmsg_pgcnt : packet->page_buf;
> > -		ret = vmbus_sendpacket_pagebuffer(out_channel,
> > -						  pgbuf,
> > -						  packet->page_buf_cnt,
> > -						  &nvmsg,
> > -						  sizeof(struct
> nvsp_message),
> > -						  req_id);
> > +		ret = vmbus_sendpacket_pagebuffer_ctl(out_channel,
> > +						      pgbuf,
> > +						      packet->page_buf_cnt,
> > +						      &nvmsg,
> > +						      sizeof(struct
> > +							     nvsp_message),
> > +						      req_id,
> > +						      vmbus_flags,
> > +						      !packet->xmit_more);
> >  	} else {
> > -		ret = vmbus_sendpacket(
> > +		ret = vmbus_sendpacket_ctl(
> >  				out_channel, &nvmsg,
> >  				sizeof(struct nvsp_message),
> >  				req_id,
> >  				VM_PKT_DATA_INBAND,
> > -
> 	VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> > +				vmbus_flags, !packet->xmit_more);
> >  	}
> >
> >  	if (ret == 0) {
> 
> This might be problematic, if queue is stopped ( netif_tx_stop_queue())
> 
> You need to force a kick if we are about to stop the queue :
> 
> Random example : commit ddd0ca5d60b350bbfbfb60b25885a9779ce6d6c7

Thanks Eric; I will fix and resend.

Regards,

K. Y
> 
>