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SubjectRe: [PLEASE-TESTME] Zerocopy networking patch, 2.4.0-1
On Tue, 9 Jan 2001, David S. Miller wrote:

> Ignore Ingo's comments about the MSG_NOCOPY flag, I've not included
> those parts in the zerocopy patches as they are very controversial
> and require some VM layer support.

Okay, I talked to some kernel engineers where I work and they were (I
think) very justifiably skeptical of zero-copy work with respect to
read/write style APIs.

> Basically, it pins the userspace pages, so if you write to them before
> the data is fully sent and the networking buffer freed, they get
> copied with a COW fault.

Yum... Assuming a gigabit ethernet link is saturated with the
sendmsg(MSG_NOCOPY) API, what is CPU utilization like for a given clock
speed and processor make? It is any different than the sendfile() case?


Dave Zarzycki

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