Re: Thread implementations...

Martin Mares (mj@atrey.karlin.mff.cuni.cz)
Thu, 25 Jun 1998 22:06:09 +0200

> > * 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.

Unless you need copying small fragments (let's say few pages) from one
file to another. In such cases mmap/munmap is just too much overhead.

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

Or maybe SCSI block copy commands, but it would be hard to implement
for anything else than block devices.

Have a nice fortnight

-- 
Martin `MJ' Mares   <mj@ucw.cz>   http://atrey.karlin.mff.cuni.cz/~mj/
Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth
"Q: Do you believe in One God? A: Yes, up to isomorphism."


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