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

To: Andrew Morton <andrewm@xxxxxxxxxx>
Subject: Re: sendfile+zerocopy: fairly sexy (nothing to do with ECN)
From: "David S. Miller" <davem@xxxxxxxxxx>
Date: Tue, 30 Jan 2001 04:52:40 -0800 (PST)
Cc: lkml <linux-kernel@xxxxxxxxxxxxxxx>, "netdev@xxxxxxxxxxx" <netdev@xxxxxxxxxxx>
In-reply-to: <3A76B72D.2DD3E640@xxxxxxxxxx>
References: <3A728475.34CF841@xxxxxxxxxx> <3A726087.764CC02E@xxxxxxxxxx> <20010126222003.A11994@xxxxxxxxxxx> <14966.22671.446439.838872@xxxxxxxxxxxxxxx> <3A76B72D.2DD3E640@xxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
Andrew Morton writes:
 > BTW: can you suggest why I'm not observing any change in NFS client
 > efficiency?

As in "filecopy speed" or "cpu usage while copying a file"?

The current fragmentation code eliminates a full SKB allocation and
data copy on the NFS file data receive path in the client, CPU has to
be saved compared to pre-zerocopy or something is very wrong.

File copy speed, well you should be link speed limited as even without
the zerocopy patches you ought to have enough cpu to keep it busy.

Later,
David S. Miller
davem@xxxxxxxxxx


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