Darren Reed wrote:
Rao Shoaib wrote:
...
The current VM provides decent support to achieve zero copy on both
send and receive. The reason networking doesn't use zero copy on send
is due to lack of appropriate interfaces and hopefully this will
change with extended socket interface. Lack of use of zero copy on
receive in networking is due to the fact that it is difficult to
implement and requires HW support which has not been present in the
NIC's.
The new VM will maintain current zero copy support (for example
segkpm). However, as is the case today, it is important to note that
the new VM will not be provide support for immutable buffers with
asynchronous semantics. This means networking interfaces for zero
copy will have to provide protection against buffer contents changing
before the buffer is consumed.
On the topic of zero-copy, what do we currently do with NFS and what
can we do?
For example, will the NFS code be able to read data from disk into a
buffer that can be attached to an mblk and sent out, without requiring
any copying?
This is possible even today using desballoca. sendfile uses this.
Rao.
Darren
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