linux-kernel - Re: [PATCH net-next v5 0/9] xen-netback: TX grant mapping with SKBTX_DEV

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Message-ID: <52E11563.1090707@citrix.com>
Date:	Thu, 23 Jan 2014 13:13:07 +0000
From:	Zoltan Kiss <zoltan.kiss@...rix.com>
To:	David Miller <davem@...emloft.net>
CC:	<ian.campbell@...rix.com>, <wei.liu2@...rix.com>,
	<xen-devel@...ts.xenproject.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <jonathan.davies@...rix.com>,
	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH net-next v5 0/9] xen-netback: TX grant mapping with SKBTX_DEV_ZEROCOPY
 instead of copy

On 23/01/14 01:50, David Miller wrote:
> From: Zoltan Kiss <zoltan.kiss@...rix.com>
> Date: Mon, 20 Jan 2014 21:24:20 +0000
>
>> A long known problem of the upstream netback implementation that on the TX
>> path (from guest to Dom0) it copies the whole packet from guest memory into
>> Dom0. That simply became a bottleneck with 10Gb NICs, and generally it's a
>> huge perfomance penalty. The classic kernel version of netback used grant
>> mapping, and to get notified when the page can be unmapped, it used page
>> destructors. Unfortunately that destructor is not an upstreamable solution.
>> Ian Campbell's skb fragment destructor patch series [1] tried to solve this
>> problem, however it seems to be very invasive on the network stack's code,
>> and therefore haven't progressed very well.
>> This patch series use SKBTX_DEV_ZEROCOPY flags to tell the stack it needs to
>> know when the skb is freed up.
>
> This series does not apply to net-next due to some other recent changes.
>
> Please respin, thanks.

It is already based on two predecessor patches, one which is already 
accepted but not applied yet:

[PATCH net-next v2] xen-netback: Rework rx_work_todo

And the other one is hopefully will be accepted very soon:

[PATCH v5] xen/grant-table: Avoid m2p_override during mapping

Zoli

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