Date: Wed, 22 Jan 2014 17:50:31 -0800 (PST)
Message-Id: <20140122.175031.873909526743971037.davem@davemloft.net>
To: zoltan.kiss@citrix.com
Cc: ian.campbell@citrix.com, wei.liu2@citrix.com,
        xen-devel@lists.xenproject.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, jonathan.davies@citrix.com
Subject: Re: [PATCH net-next v5 0/9] xen-netback: TX grant mapping with
 SKBTX_DEV_ZEROCOPY instead of copy
From: David Miller <davem@davemloft.net>
In-Reply-To: <1390253069-25507-1-git-send-email-zoltan.kiss@citrix.com>
References: <1390253069-25507-1-git-send-email-zoltan.kiss@citrix.com>
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From: Zoltan Kiss <zoltan.kiss@citrix.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.

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