In message <[EMAIL PROTECTED]>, Ju
lian Elischer writes:

>Bill Jolitz had a plan for 386BSD where all the buffers were nearly
>always unmapped from KVM. He was going to have a number of slots
>available for mapping them which would be used in a lifo order

This entire area needs to be rethought.

And by "rethought" I really mean try to redesign it from scratch
to match our current needs and see what that leads to compared to
the stuff we have.

On of my first TODO after the 5.x/6.x branch is to give struct bio
the ability to communicate in a vector of separate pages, not
necessarily mapped.  This gives us a scatter gather ability in 
the entire disk I/O path.

This opens up a host of possibilities for things like clustering,
background writes (using copy-on-write pages) etc etc etc.

Needless to say, it will also drastically change the working
environment for struct buf.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED]         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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