Max size of swapspace - 2GB?

[James Knott]

Lennart Sorensen wrote:
> On Mon, Aug 22, 2005 at 02:53:34PM -0400, Fraser Campbell wrote:
>>I have been creating >2GB swapspaces for quite a while.  Recently I read 
>>the manpage:
>>
>>    The maximum useful size of a swap area now depends on the
>>    architecture.  It is roughly  2GiB on  i386,  PPC,  m68k, ARM, 1GiB
>>    on sparc, 512MiB on mips, 128GiB on alpha and 3TiB on sparc64.
>>
>>As a test I just created a 3GB swapspace (single logical volume) and 
>>then had a few programs suck up all the RAM.  I saw 3GB of real RAM used 
>>and 3GB of swapspace used before the server ran out of memory.
>>
>>Based on my test I assume that the manpage is just out of date, or am I 
>>missing something?  My test was with 2.6.5 kernel (SuSE 9).
> 
> The man pages often become out of date.  I think this is such a case.  I
> believe 2.6 kernels can handle much larger than 2GB swap space.  On the
> other hand I can't imagine how awful the system must run when it is
> using even 1GB of swap. :)

That would depend on how often you're hitting the swap.  If it's simply
holding a lot of recently, but not currently accessed stuff, it could
have decent performance.  I seem to recall reading that it's often
faster to pull data from swap, than to re-load from disk.
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