netdev - Re: Generalizing mmap'ed sockets

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Date:	Fri, 19 Nov 2010 14:10:05 -0800
From:	Andrew Grover <andy.grover@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: Generalizing mmap'ed sockets

On Fri, Nov 19, 2010 at 12:04 PM, Tom Herbert <therbert@...gle.com> wrote:
> This is a project I'm contemplating.  If you have any comments or can
> point me to prior work in this area that would be appreciated.

> TX:
>  - Zero copy transmit (which is already supported by vmsplice(), but
> this might be simpler)
>  - One system call needed on transmit which can cover multiple
> datagrams or what would have been multiple writes (the call is just to
> kick kernel to start sending)

I'd look at our existing recvmmsg syscall -- there was talk of doing a
sendmmsg, which sounds close to what you want.

> RX:
>  - Zero system calls needed to do receive (determining data ready is
> accomplished by polling)
>  - Immediate data placement in kernel available all the time,
> including OOO placement
>  - Potential for true zero copy on receive with device support (like
> per flow queues, UDP queues)

Mentioning zero-copy per-flow queues in userspace suggests Infiniband
is prior work in this area.

Regards -- Andy
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