Re: [PATCH net-next v5 0/9] xen-netback: TX grant mapping with SKBTX_DEV_ZEROCOPYinstead of copy

From: Zoltan Kiss
Date: Thu Jan 23 2014 - 08:13:23 EST

On 23/01/14 01:50, David Miller wrote:
From: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
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


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