netdev - [PATCH net-next v2 0/2] net: mvneta: improve rx performance

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Date:   Fri, 17 Feb 2017 18:02:31 +0800
From:   Jisheng Zhang <jszhang@...vell.com>
To:     <thomas.petazzoni@...e-electrons.com>, <davem@...emloft.net>,
        <arnd@...db.de>
CC:     <linux-arm-kernel@...ts.infradead.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Jisheng Zhang <jszhang@...vell.com>
Subject: [PATCH net-next v2 0/2] net: mvneta: improve rx performance

In hot code path such as mvneta_rx_hwbm() and mvneta_rx_swbm(), we may
access fields of rx_desc. The rx_desc is allocated by
dma_alloc_coherent, it's uncacheable if the device isn't cache
coherent, reading from uncached memory is fairly slow.

patch1 reuses the read out status to getting status field of rx_desc
again.

patch2 uses cacheable memory to store the rx buffer DMA address.

We get the following performance data on Marvell BG4CT Platforms
(tested with iperf):

before the patch:
recving 1GB in mvneta_rx_swbm() costs 149265960 ns

after the patch:
recving 1GB in mvneta_rx_swbm() costs 1421565640 ns

We saved 4.76% time.

RFC: can we do similar modification for tx? If yes, I can prepare a v2.

Basically, these two patches do what Arnd mentioned in [1].

Hi Arnd,

I added "Suggested-by you" tag, I hope you don't mind ;)

Thanks

[1] https://www.spinics.net/lists/netdev/msg405889.html

Since v1:
  - correct the performance data typo

Jisheng Zhang (2):
  net: mvneta: avoid getting status from rx_desc as much as possible
  net: mvneta: Use cacheable memory to store the rx buffer DMA address

 drivers/net/ethernet/marvell/mvneta.c | 36 ++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

-- 
2.11.0