netdev - RE: [PATCH 1/1] Drivers: net-next: hyperv: Adjust the size of sendbuf region to support ws2008r2

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Date:	Wed, 6 Aug 2014 17:25:11 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Jeff Leung <jleung@...networks.ca>,
	"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 1/1] Drivers: net-next: hyperv: Adjust the size of sendbuf
 region to support ws2008r2



> -----Original Message-----
> From: Jeff Leung [mailto:jleung@...networks.ca]
> Sent: Wednesday, August 6, 2014 10:19 AM
> To: KY Srinivasan; 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 1/1] Drivers: net-next: hyperv: Adjust the size of
> sendbuf region to support ws2008r2
> 
> > WS2008R2 is a supported platform and it turns out that the maximum
> sendbuf
> > size that ws2008R2 can support is only 15MB. Make the necessary
> > adjustment.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > ---
> >  drivers/net/hyperv/hyperv_net.h |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/net/hyperv/hyperv_net.h
> b/drivers/net/hyperv/hyperv_net.h
> > index 40ba1ef..459b823 100644
> > --- a/drivers/net/hyperv/hyperv_net.h
> > +++ b/drivers/net/hyperv/hyperv_net.h
> > @@ -584,7 +584,7 @@ struct nvsp_message {
> >
> >  #define NETVSC_RECEIVE_BUFFER_SIZE		(1024*1024*16)
> 	/* 16MB
> > */
> >  #define NETVSC_RECEIVE_BUFFER_SIZE_LEGACY	(1024*1024*15)  /*
> 15MB
> */
> > -#define NETVSC_SEND_BUFFER_SIZE			(1024 * 1024 *
> 16)   /* 16MB */
> > +#define NETVSC_SEND_BUFFER_SIZE			(1024 * 1024 *
> 15)   /* 15MB */
> 
> Would it be possible to use separate ifdefs depending on the version of the
> Hyper-V host so we can maintain the 16MB buffer for hosts that support it
> and leave it at 15MB for hosts that don't support that large of a buffer?

We could certainly do that. For the receive buffers, we actually size them based on the host.
For sendbuf, the performance difference between 15M and 16M is not measurable. I had initially
chosen 16MB to match with the receive buffer size. Since there was no perf advantage, I chose to
set the sendbuf size to 15M to work on all supported hosts.

K. Y 
> 
> >  #define NETVSC_INVALID_INDEX			-1
> >
> >
> > --
> > 1.7.4.1
> >
> > --
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