[PATCH 0/6] staging: fsl-dpaa2/eth: Frame buffer optimizations

[Ioana Radulescu]

This patchset continues the work related to frame buffer layout.

The first two patches fix an issue and simplify some rather convoluted
formulas introduced by a previous commit.

The third adds a new counter for TX skb reallocations due to
insufficient headroom. This helped us notice that most of the frames
originated on the core had skbs with too little headroom, leading to
additional alloc/free operations and a performance penalty for
egress termination traffic.

A closer look at hardware requirements vs recommandations showed
that we don't in fact need to be so strict with our TX buffer layout.
The last three patches in this set remove all restrictions that are
not mandatory from a functional standpoint, lowering the required
TX headroom from 192B to 64B.

This helps avoid realloc's for most TCP frames. On a LS2088A board
with one core @2GHz, running a netperf TCP_SENDFILE test (as client),
we see an increase in throughput from 3.79Gbps to 5.11Gbps. For UDP
traffic no improvement is observed, since the stack usually creates
skbs with minimal headroom (2B) for UDP frames.

Ioana Radulescu (6):
  staging: fsl-dpaa2/eth: Fix access to FAS field
  staging: fsl-dpaa2/eth: Don't set netdev->needed_headroom
  staging: fsl-dpaa2/eth: Add counter for skb reallocs
  staging: fsl-dpaa2/eth: Don't enable FAS on Tx
  staging: fsl-dpaa2/eth: Compute needed headroom per frame
  staging: fsl-dpaa2/eth: Make Tx buffer alignment optional

 drivers/staging/fsl-dpaa2/ethernet/dpaa2-eth.c     | 111 +++++----------------
 drivers/staging/fsl-dpaa2/ethernet/dpaa2-eth.h     |  31 +++---
 drivers/staging/fsl-dpaa2/ethernet/dpaa2-ethtool.c |   1 +
 3 files changed, 46 insertions(+), 97 deletions(-)

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2.7.4