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

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Date:   Fri, 17 Feb 2017 11:37:21 +0100
From:   Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:     Jisheng Zhang <jszhang@...vell.com>
Cc:     <thomas.petazzoni@...e-electrons.com>, <davem@...emloft.net>,
        <arnd@...db.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH net-next v2 0/2] net: mvneta: improve rx performance

Hi Jisheng,

 On ven., févr. 17 2017, Jisheng Zhang <jszhang@...vell.com> wrote:

> 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.

Did you test it with HWBM support?

I am  not sure ti will work in this case.

Gregory

>
> 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
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

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