On Sat, Jul 06, 2002 at 02:37:02PM -0700, Darren Pilgrim wrote:
> Bernd Walter wrote:
> > On Fri, Jul 05, 2002 at 05:58:15PM -0700, Darren Pilgrim wrote:
> > > If RAM + swap can be more than 4GB, how does FreeBSD address swap on a
> > > 32-bit machine?  Does the kernel internally use a wider address space
> > 
> > The same way it does on every partitition: using block numbers.
> > That way you can address 1TByte.
> 
> I thought the limit for filesystems was 2TB?

The Blocknumber is signed that gives:
2^31 * 512Bytes

> > And you can have more than a single swap partition.
> 
> Up to four, so then the theoretical limit for swap is 8TB?

4 is just a default.
[61]cicely9# swapinfo
Device          1K-blocks     Used    Avail Capacity  Type
/dev/da1b          105472       80   105392     0%    Interleaved
/dev/da11b         174880        0   174880     0%    Interleaved
/dev/da4b          211456        0   211456     0%    Interleaved
/dev/da5b          211456        0   211456     0%    Interleaved
/dev/da6b          211456        0   211456     0%    Interleaved
/dev/da7b          211456        0   211456     0%    Interleaved
/dev/da8b          211456        0   211456     0%    Interleaved
/dev/da9b          211456        0   211456     0%    Interleaved
/dev/da10b         211456        0   211456     0%    Interleaved
Total             1760544       80  1760464     0%

The limit here is the maximum number of harddisks, which is IIRC 512
per driver.
This cames from the available minor bits in the device node.

> > In reality managementstructures which have to be in kernel addressspace
> > is limiting swap before.
> 
> Do these management structures grow as swap grows, or do they only
> change as the utilization increases?

AFAIK there is a static part.
Possible not memory but only KVM addressspace.
Also AFAIK it makes a difference if you allocate the same space
using a single partition or in more than one.

-- 
B.Walter              COSMO-Project         http://www.cosmo-project.de
[EMAIL PROTECTED]         Usergroup           [EMAIL PROTECTED]


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