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Date:      Thu, 15 Apr 1999 14:38:37 -0400 (EDT)
From:      Mikhail Teterin <mi@misha.cisco.com>
To:        dillon@apollo.backplane.com (Matthew Dillon)
Cc:        current@freebsd.org
Subject:   Re: swap on Irix (overcommiting, etc.)
Message-ID:  <199904151838.OAA98565@misha.cisco.com>
In-Reply-To: <199904151808.LAA47676@apollo.backplane.com> from Matthew Dillon at "Apr 15, 1999 11:08:52 am"

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Matthew Dillon once wrote:
> :On Irix, each swap area has the following parameter (from swap(1M)):
> :
> :  vswap   The size the system believes the area can hold.  This is
> :	  always greater than or equal to pswap and maxswap.
> :
> :This way, an administrator can control the amount of overcommited
> :memory (making it 0 if neccessary). It may be sufficient to have this
> :as a centralized parameter, rather then a per swap area.

 
>     I think they finally got rid of vswap in later IRIX's after they
>     fixed the core swapping code to 'overcommit'.  The reality behind
>     the virtual swap concept w/ IRIX is based on issues with the original
[...]

Mmm, that's how they use(d) it then... But can we have a way for an
admin to control the amount of overcommited memory? Ranging from 0 -- no
overcommitment to the entire addressable space less the phisical storage
(the current situation)... And this is different from the per-user class
limit.

I guess, I'd settle for being able to specify the per-user class:

	. datasize limit in percents of the total available RAM+swap
	. kill-order, so the kernel will start killing with the least
	  important users (and services running in their own sandboxes)

Does not fix the non-compliance with ANSI, strictly speaking...

>     FreeBSD does it right - it only allocates swap when it needs to
>     swap something out of main memory. The total available VM is
>     essentially the amount of main memory plus the amount of swap
>     (non-inclusive of mmap()'d files which do not take any swap at
>     all).

FreeBSD is perfect for my existing needs...

> :They also have priorities of the swap areas (only swap here when
> :areas with higher priorities are full), and an ability to stop
> :paging onto a particular area. Mmmm...

What about this two?

	-mi


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