Thanks guys, for explaining the swap system to me. I have a good
understanding of how the system works now. I want to particularly
thank Matthew Dillon for taking the time to lay down the technical
details as he did. Being able to ask a question like this and get it
answered so well is what put
:Is NSWAP tied to the NSWAPDEV kernel option, or is it the actual number
:of active swap devices? If the prior, is setting NSWAPDEV to the
:actual number of swap devices a useful for improving memory usage? Is
:NSWAPDEV just a compile-time tunable, or is there a sysctl to do the
:same thing?
Matthew Dillon wrote:
> The nominal limit for swap space is around 14 GB due to limitations
> in available KVM. There are three major limiting factors in the kernel:
>
> * The swap bitmap eats 2 bits per page of swap. The bitmap is sized
> to handle NSWAP (default 4) x size_of
On Sat, Jul 06, 2002 at 05:33:50PM -0700, Matthew Dillon wrote:
>
> :
> :On Sat, Jul 06, 2002 at 04:42:22PM -0700, Matthew Dillon wrote:
> :> Negative block numbers are used by UFS to represent the indirect blocks
> :> associated with a file, while positive block numbers represent the
> :
In message <[EMAIL PROTECTED]>, Bernd Walter writes:
>I never saw any negative block numbers in on-disc structures.
>Now I wonder if it was just hidden behind macros.
>What is the reason to handle it that way?
>Do you have some code reference for homework?
These logical block numbers are not stor
:> >
:> > Physical block numbers are 512-byte sized, with a range of 2^32
:> > in -stable. This also winds up being 2TB. So increasing the fragment
:> > size does not help in -stable.
:>
:> It's a proven fact that there is a 1T limit somewhere which was
:> explained with physical b
On Sun, Jul 07, 2002 at 02:10:19AM +0200, Bernd Walter wrote:
> On Sat, Jul 06, 2002 at 04:42:22PM -0700, Matthew Dillon wrote:
> > Negative block numbers are used by UFS to represent the indirect blocks
> > associated with a file, while positive block numbers represent the
> > content
:
:On Sat, Jul 06, 2002 at 04:42:22PM -0700, Matthew Dillon wrote:
:> Negative block numbers are used by UFS to represent the indirect blocks
:> associated with a file, while positive block numbers represent the
:> contents of the file.
:
:I never saw any negative block numbers in on-
On Sat, Jul 06, 2002 at 04:42:22PM -0700, Matthew Dillon wrote:
> Negative block numbers are used by UFS to represent the indirect blocks
> associated with a file, while positive block numbers represent the
> contents of the file.
I never saw any negative block numbers in on-disc stru
Negative block numbers are used by UFS to represent the indirect blocks
associated with a file, while positive block numbers represent the
contents of the file.
These are logical block numbers, which are fragment-sized (1K typically).
So, 2^31 x 1K = 2TB.
Physical block n
:...
:>
:> Up to four, so then the theoretical limit for swap is 8TB?
:
:I hope not, since I have 6 of 'em. 4's just the default.
:
:
:> Do these management structures grow as swap grows, or do they only
:> change as the utilization increases?
:
:I believe they're pre-allocated, so it's the siz
On Sat, Jul 06, 2002 at 04:01:18PM -0700, Terry Lambert wrote:
> Darren Pilgrim wrote:
> > > > I thought the limit for filesystems was 2TB?
> > >
> > > The Blocknumber is signed that gives:
> > > 2^31 * 512Bytes
> >
> > Why sign the blocknumber? LBA uses an unsigned 32-bit integer,
> > allowing
On Sat, Jul 06, 2002 at 03:43:00PM -0700, Darren Pilgrim wrote:
> Bernd Walter wrote:
> > 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,
Darren Pilgrim wrote:
> > > I thought the limit for filesystems was 2TB?
> >
> > The Blocknumber is signed that gives:
> > 2^31 * 512Bytes
>
> Why sign the blocknumber? LBA uses an unsigned 32-bit integer,
> allowing 2TB, and IIRC SCSI uses an unsigned integer as well (though I
> can't remember
Bernd Walter wrote:
> 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 kerne
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 addre
On Sat, Jul 06, 2002 at 02:37:02PM -0700 I heard the voice of
Darren Pilgrim, and lo! it spake thus:
>
> > And you can have more than a single swap partition.
>
> Up to four, so then the theoretical limit for swap is 8TB?
I hope not, since I have 6 of 'em. 4's just the default.
> Do these ma
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 num
: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
:with some kind of translation to 32-bit space for programs and hardware
:that can't handle 64-bit addresses or does it not map swap into the
:address spa
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
> with some kind of translation to 32-bit space for programs and hardware
> that can't handle 64-bit addresses or does it not map s
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
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
with some kind of translation to 32-bit space for programs and hardware
that can't handle 64-bit addresses or does it not map swap into the
address space at
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