Re: RE: on load control / process swapping

[Rik van Riel <riel@conectiva.com.br>]

On Wed, 16 May 2001, Matt Dillon wrote:

>     In regards to the particular case of scanning a huge multi-gigabyte
>     file, FreeBSD has a sequential detection heuristic which does a
>     pretty good job preventing cache blow-aways by depressing the priority
>     of the data as it is read or written.  FreeBSD will still try to cache
>     a good chunk, but it won't sacrifice all available memory.  If you
>     access the data via the VM system, through mmap, you get even more
>     control through the madvise() syscall.

There's one thing "wrong" with the drop-behind idea though;
it penalises data even when it's still in core and we're
reading it for the second or third time.

Maybe it would be better to only do drop-behind when we're
actually allocating new memory for the vnode in question and
let re-use of already present memory go "unpunished" ?

Hmmm, now that I think about this more, it _could_ introduce
some different fairness issues. Darn ;)

regards,

Rik
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