linux-kernel - RE: [PATCH net-next] hyperv: Add support for physically discontinuous receive buffer

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Date:	Mon, 27 Jan 2014 21:47:43 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	KY Srinivasan <kys@...rosoft.com>,
	David Miller <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>
Subject: RE: [PATCH net-next] hyperv: Add support for physically
 discontinuous receive buffer



> -----Original Message-----
> From: KY Srinivasan
> Sent: Monday, January 20, 2014 5:11 PM
> To: Haiyang Zhang; David Miller
> Cc: netdev@...r.kernel.org; olaf@...fle.de; jasowang@...hat.com; linux-
> kernel@...r.kernel.org; driverdev-devel@...uxdriverproject.org
> Subject: RE: [PATCH net-next] hyperv: Add support for physically discontinuous
> receive buffer
> 
> 
> 
> > -----Original Message-----
> > From: Haiyang Zhang
> > Sent: Monday, January 20, 2014 2:06 PM
> > To: David Miller
> > Cc: netdev@...r.kernel.org; KY Srinivasan; olaf@...fle.de;
> > jasowang@...hat.com; linux-kernel@...r.kernel.org; driverdev-
> > devel@...uxdriverproject.org
> > Subject: RE: [PATCH net-next] hyperv: Add support for physically
> > discontinuous receive buffer
> >
> >
> >
> > > -----Original Message-----
> > > From: David Miller [mailto:davem@...emloft.net]
> > > Sent: Tuesday, January 14, 2014 5:32 PM
> > > To: Haiyang Zhang
> > > Cc: netdev@...r.kernel.org; KY Srinivasan; olaf@...fle.de;
> > > jasowang@...hat.com; linux-kernel@...r.kernel.org; driverdev-
> > > devel@...uxdriverproject.org
> > > Subject: Re: [PATCH net-next] hyperv: Add support for physically
> > > discontinuous receive buffer
> > >
> > > From: Haiyang Zhang <haiyangz@...rosoft.com>
> > > Date: Thu,  9 Jan 2014 14:24:47 -0800
> > >
> > > > This will allow us to use bigger receive buffer, and prevent
> > > > allocation failure due to fragmented memory.
> > > >
> > > > Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> > > > Reviewed-by: K. Y. Srinivasan <kys@...rosoft.com>
> > >
> > > Not until you start using paged SKBs in netvsc_recv_callback.
> > >
> > > Whatever fragmention you think you're avoiding in the hyperv layer,
> > > you're still going to get from the:
> > >
> > > skb = netdev_alloc_skb_ip_align(net, packet->total_data_buflen);
> > >
> > > call there.
> > >
> > > This change makes no sense in isolation, therefore I'm not applying
> > > it until you also include the appropriate changes to avoid the same
> > > exact fragmentation issue in netvsc_drv.c as stated above.
> >
> > The receive buffer currently requires multiple MB of physically
> > continuous memory, and may fail to be allocated when memory is
> > fragmented. The patch is created for this issue.
> >
> > The SKB buffer is usually less than 1500 bytes or up to several KB
> > with jumbo frame, so it's much less sensitive to fragmented memory. I
> > will work on another patch to use SKB buffer with discontinuous pages.
> >
> > Could you accept this patch separately?
> 
> Today, if we try to unload and load the network driver, the load may fail
> because we may not be able to allocate the receive buffers if memory is
> fragmented. This patch specifically addresses this problem.
> 
> Regards,
> 
> K. Y

Dave,

So, could this patch be taken first?

Thanks,
- Haiyang

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