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SubjectRe: Thread implementations...
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>    What about adding a syscall to _copy_ data from one file descriptor
> to another one, supporting not only sockets, but also plain files.

I can think of only one reason to do this

> * File blocks can be copied without passing them to/from user
> space.

mmap()

> * With some support in file systems, we can convert block-aligned
> copies directly to buffer cache operations, potentially using
> SCSI block copy operations).

mmap()

> * We can also implement socket-to-file, file-to-pipe and several
> other interesting cases without introducing YAS (Yet Another
> Syscall).

mmap a file and send via socket(). Thats basically doing blast buffer
cache to wire. It wont speed up much.

Now the reason to have it is for NFS type systems that support copy
and copytree operations directly on the remote (eg SMB)

Alan


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