From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: "ustc.mail" <backyes@mail.ustc.edu.cn>
Cc: linux-pci@vger.kernel.org, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: 【Question】Whether it's legal to enable same physical DMA memory mapped for different NIC device?
Date: Tue, 3 Jan 2012 15:33:57 -0500 [thread overview]
Message-ID: <20120103203357.GD17472@phenom.dumpdata.com> (raw)
In-Reply-To: <CAJULonj9rFDKNCzpEXj2r3XjkYojy-CGYpVQ1RF8SxwLVrXqAA@mail.gmail.com>
On Wed, Dec 07, 2011 at 10:16:40PM +0800, ustc.mail wrote:
> Dear all,
>
> In NIC driver, to eliminate the overhead of dma_map_single() for DMA
> packet data, we have statically allocated huge DMA memory buffer ring
> at once instead of calling dma_map_single() per packet. Considering
> to further reduce the copy overhead between different NIC(port) ring
> while forwarding, one packet from a input NIC(port) will be
> transferred to output NIC(port) with no any copy action.
>
> To satisfy this requirement, the packet memory should be mapped into
> input port and unmapped when leaving input port, then mapped into
> output port and unmapped later.
>
> Whether it's legal to map the same DMA memory into input and output
> port simultaneously? If it's not, then the zero-copy for packet
> forwarding is not feasible?
>
Did you ever a get a response about this?
Is the output/input port on a seperate device function? Or is it
just a specific MMIO BAR in your PCI device?
> Hope PCI expert to post your suggestion.
>
> Thanks!
>
> --Yanfei
>
> --
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next prev parent reply other threads:[~2012-01-03 20:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-07 14:16 【Question】Whether it's legal to enable same physical DMA memory mapped for different NIC device? ustc.mail
2012-01-03 20:33 ` Konrad Rzeszutek Wilk [this message]
2012-01-04 2:44 ` Yanfei Wang
2012-01-04 15:59 ` James Bottomley
2012-01-05 12:40 ` Yanfei Wang
2012-01-05 16:20 ` James Bottomley
2012-01-06 2:05 ` Yanfei Wang
2012-01-06 16:00 ` James Bottomley
2012-01-05 18:48 ` Don Dutile
2012-01-06 2:11 ` Yanfei Wang
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