Re: Swap support

[Harry Kalogirou <harkal@gmx.net>]

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Την Δευ, 22-04-2002 στις 16:42, ο/η Javier Sedano έγραψε:
> Harry Kalogirou wrote:
> > 
> '> Yesterday I commited to the CVS some experimental swap support code,
> > based on Alan's work on the subject. Ofcourse this code is not included
> > in the default configuration and is not for _actual_ use, since as I
> > said is experimental. Apart from that if you set the swap partition in
> > malloc.c you and enable swapping you can enjoy an 8086 system use
> > _virtual_ memory!
> > 
> 
> 	Great!
> 
> 	I've been looking for it in the code, and found nothing about it's
> configuration (setting the partition and the size, activating it...)...
> can someone (Harry, Alan) give us a few words about how to do so?

I will focus on making it easily configurable at run time later along
with documenting it a bit. Basicaly the code now is a 4 hour brain
storm. To configure it you basicaly change this part of the code :


	holep = &swap_holes[0];
	holep->flags = HOLE_FREE;
	holep->page_base = 0;
	holep->extent = 128;
	holep->refcount = 0;
	holep->next = NULL;

	swap_dev = 0x0100;

The extent is the size in kilobytes and the swap_dev is the block device
to swap to. In the example 0x0100 is /dev/ram0


> 	And by the way... can you write a technical description about how is it
> done? The main problem with swap in minix was (is) that processes

It's on my TODO list...

> waiting for IO (waiting for a message from FS) can not be swapped in,
> because they would meet a deadlock when trying to swap out (for FS is
> needed again to do the swapping out, but it is frozen sending the
> message to the process, because FS is not reentrant/concurrent in
> minix)... and obviously processes waiting for IO are those best suited
> to be swapped in.
> 

As you might already noticed we don't use the FS layer, we only support
swapping to a device at the momment. Once the think works we can add
swapping to file easily. For the minix matter now - our FS is reentrant
so we will have no problem...

Harry


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