Messages in this thread | | | From | Hemment_Mark/ | Date | Thu, 25 Apr 96 16:16:34 +0100 | Subject | Re: page tables |
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Hi,
From: mingo/UNIX (mingo@pc5829.hil.siemens.co.at) Date: ## 04/25/96 12:24 ## > > On Thu, 25 Apr 1996 > > Hemment_Mark/HEMEL_IOPS_INTERNATIONAL-SALES@uniplex.co.uk wrote: > > > > the _minimum_ that is being used for page tables by user processes > > is 20*2 = 40 pages (160KB). Ok, thats not v. large, but some of those > > processes spent alot of time asleep (hours maybe). Why should they be > > allowed to hold on to a valuable resource which they are not using?
> 160KByte ... unless there is an elegant way to do it without loosing > cycles in the page fault handler ... no way! :) I would rather use my > shadow memory then :))))
Ok, so if a secondary page table for a process (that has been idle for sometime) needs to be faulted in, that's one extra fault on the first reference to the 4MB range it covers. That's not much of an overhead...
While the page table(s) are out, the released page(s) are available for other uses. As more free memory is available to the system it _should_ reduce the need to page-out (and fault back in again) other pages which are more more frequently referenced than those table pages.
It's a balancing act - taking a resource from where it is not being used effectively, and giving it to another area that can use it better.
The problem is getting the balance right (espically on a Friday night...:)
markhe
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