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Re: sendfile+zerocopy: fairly sexy (nothing to do with ECN)

To: Ion Badulescu <ionut@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: sendfile+zerocopy: fairly sexy (nothing to do with ECN)
From: Andrew Morton <andrewm@xxxxxxxxxx>
Date: Sat, 27 Jan 2001 21:45:29 +1100
Cc: lkml <linux-kernel@xxxxxxxxxxxxxxx>, "netdev@xxxxxxxxxxx" <netdev@xxxxxxxxxxx>, Aaron Lehmann <aaronl@xxxxxxxxxxx>
References: <3A728475.34CF841@xxxxxxxxxx> <200101271009.f0RA9fb04363@xxxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
Ion Badulescu wrote:
> 
> On Sat, 27 Jan 2001 19:19:01 +1100, Andrew Morton <andrewm@xxxxxxxxxx> wrote:
> 
> > The figures I quoted for the no-hw-checksum case were still
> > using scatter/gather.  That can be turned off as well and
> > it makes it a tiny bit quicker.
> 
> Hmm. Are you sure the differences are not just noise?

I don't think so.  It's all pretty repeatable.

> Unless you
> modified the zerocopy patch yourself, it won't use SG without
> checksums...

I believe it in fact does use SG when hardware tx checksums are unavailable,
but this capability wil be removed RSN because userspace can scribble
on the pagecache after the checksum has been calculated, and before
the frame has hit the wire.

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