🚀 go-pugleaf

Alan Bellingham <alanb@episys.com> wrote:

>Entirely the opposite - it allows you to ask the operating system to
>pretend the disk is RAM - but at the same time, to use its best caching
>algorithms to ensure disk is only read or written when it can't avoid
>it.

As an aside: many years ago, I went to a presentation on the design of
Windows NT. What surprised me was that the whole OS is designed to work
in paged memory, and it was theoretically possible to run it in (I think
it was) 12K of RAM.

Yes, that was kilobytes, not megabytes. Nearly an order of magnitude
less memory than the then current DOS systems required.

Admitted, it would be catastrophically slow with that little RAM. But
what happened when you added more RAM was that more of the disk was
getting cached. About the only  part of the OS that couldn't be swapped
out to disk was the code that ... swapped the chunks of OS out to disk.
Once you had as much RAM as the 'working set', it had reached full speed
and couldn't get any faster, simply because by then it never reached the
conditions when it need to save memory to disk any more.

Alan Bellingham
-- 
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