[CST-1b] OS Funcs - 97.4.7

[Chris Wilson]

Hows this for a few more:

How about when memory gets low, have the scheduler hand out CPU time in
bigger chunks (subject to any real-time requirements etc).

Also allow applications to specify which of their pages are less important
and can be paged to disk.

Swap low priority processes to disk.

If disk is idle some of the time then write lots of pages out to disk but
leave them in memory - then if you actually need to page them later it's
probably just a case of changing one bit in the page table so finding a
slot to page something back into memory will not require a disk-write
first. (I think this is what Sapna means by pre-cleaning below).

I'm sure there are lots more ;-)

Chris.

> 1) have a good page replacement algorithm (actually this isn't that good
> on it's own... see others...)

> 2) use "pre-cleaning" - where you write back all modified pages to disk so
> that if any need to be replaced they can be (ie no dirty bit will be set
> for them)

In disk idle time I presume?

> 3) prepaging, and also
> 3.5)  throw out processes that can't get their working set

Swapping as opposed to paging.

> 4) use buffering - don't wait until a page has been thrown out so you can
> replace it, put the page you want into a buffer and read it 
> 5)use access controls to choose replacement pages
> 
> i'm sure others will add more or disagree with me :-)
> 
> regards
> Sapna
> ------------------------------------
> 
> On Wed, 31 May 2000, Nathan Dimmock wrote:
> 
> > OS Funcs - 97.4.7.  List 5 techniques that can be used in an OS to
> > improve the performance of demand paged virtual memory.
> > 
> > The only one I could think of is pre-paging. :(  Can anyone give me a
> > clue about the rest, please?
> > 
> > TIA
> > -- 
> > Nathan 
> > Jesus College, Cambridge, CB5 8BL
> > http://www-jcsu.jesus.cam.ac.uk/~ned21/
> > 
> > 
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> 
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