Re: [PATCH][RFC 23/23]: Support for zero-copy TCP transmit of userspace data

From: Jeremy Fitzhardinge
Date: Fri Dec 19 2008 - 20:56:31 EST


Evgeniy Polyakov wrote:
Shared info is freed when there are no skbs referring to the shared info
in question. Skb holds all pages in shared info in the fraglist array,
so when it is about to be freed, it means that network stack does not
use it (particulary it will putpage every page in fraglist). Usually
there are two skbs in the network stack per packet in TCP (allocated at
once though via fastclone mechanims): one is provided to the device
(and will be freed there) and another one is placed into retransmit
queue, where it will be located and freed when ack has been received.

There may be another layers which may clone skb, but its shared info
structure (shared between the clones) will only be freed when all users
freed appropriate cloned skbs.

I see. One more question: how would I go about submitting some data with the callback attached to it?

J
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